| CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($)
 | Total | Common Stock | Additional Paid-In Capital | Treasury Stock | Accumulated Deficit | 
| Beginning balance at Apr. 30, 2019 | $ 26,461,428 | $ 18,666 | $ 68,562,727 | $ (70,000) | $ (42,049,965) | 
| Beginning balance (in shares) at Apr. 30, 2019 | Ìý | 18,665,551 | Ìý | Ìý | Ìý | 
| Increase (Decrease) in Stockholders' Equity [Roll Forward] | Ìý | Ìý | Ìý | Ìý | Ìý | 
| Stock-based compensation | 1,627,304 | Ìý | 1,627,304 | Ìý | Ìý | 
| Common stock issued for cashless stock options exercised | 0 | $ 191 | (191) | Ìý | Ìý | 
| Common stock issued for cashless stock options exercised (in shares) | Ìý | 190,559 | Ìý | Ìý | Ìý | 
| Common stock issued for stock options exercised for cash | 768,381 | $ 234 | 768,147 | Ìý | Ìý | 
| Common stock issued for stock options exercised for cash (in shares) | Ìý | 234,233 | Ìý | Ìý | Ìý | 
| Common stock issued for cashless warrant exercise | 0 | $ 77 | (77) | Ìý | Ìý | 
| Common stock issued for cashless warrant exercise (in shares) | Ìý | 76,929 | Ìý | Ìý | Ìý | 
| Amortization of warrant based cost | 27,690 | Ìý | 27,690 | Ìý | Ìý | 
| Amortization of restricted stock issued for services | 97,748 | Ìý | 97,748 | Ìý | Ìý | 
| Restricted stock issued for services, subject to vesting | 0 | $ 144 | (144) | Ìý | Ìý | 
| Restricted Stock Issued for Services, subject to vesting (in shares) | Ìý | 144,803 | Ìý | Ìý | Ìý | 
| Common stock issued for equity raise, net of underwriter costs | 16,044,879 | $ 2,415 | 16,042,464 | Ìý | Ìý | 
| Common stock issued in equity raise, net of underwriter costs (in shares) | Ìý | 2,415,000 | Ìý | Ìý | Ìý | 
| Other offerings costs | (51,282) | Ìý | (51,282) | Ìý | Ìý | 
| Beneficial conversion feature on convertible debt | 1,692,309 | Ìý | 1,692,309 | Ìý | Ìý | 
| Common stock short swing reclamation | 5,433 | Ìý | 5,433 | Ìý | Ìý | 
| Net loss | (4,994,502) | Ìý | Ìý | Ìý | (4,994,502) | 
| Ending balance at Jan. 31, 2020 | 41,679,388 | $ 21,727 | 88,772,128 | (70,000) | (47,044,467) | 
| Ending balance (in shares) at Jan. 31, 2020 | Ìý | 21,727,075 | Ìý | Ìý | Ìý | 
| Beginning balance at Oct. 31, 2019 | 24,967,090 | $ 19,142 | 69,781,363 | (70,000) | (44,763,415) | 
| Beginning balance (in shares) at Oct. 31, 2019 | Ìý | 19,142,316 | Ìý | Ìý | Ìý | 
| Increase (Decrease) in Stockholders' Equity [Roll Forward] | Ìý | Ìý | Ìý | Ìý | Ìý | 
| Stock-based compensation | 737,820 | Ìý | 737,820 | Ìý | Ìý | 
| Common stock issued for cashless stock options exercised | 0 | $ 9 | (9) | Ìý | Ìý | 
| Common stock issued for cashless stock options exercised (in shares) | Ìý | 8,352 | Ìý | Ìý | Ìý | 
| Common stock issued for stock options exercised for cash | 530,668 | $ 121 | 530,547 | Ìý | Ìý | 
| Common stock issued for stock options exercised for cash (in shares) | Ìý | 121,407 | Ìý | Ìý | Ìý | 
| Amortization of warrant based cost | 9,125 | Ìý | 9,125 | Ìý | Ìý | 
| Amortization of restricted stock issued for services | 24,398 | Ìý | 24,398 | Ìý | Ìý | 
| Restricted stock issued for services, subject to vesting | 0 | $ 40 | (40) | Ìý | Ìý | 
| Restricted Stock Issued for Services, subject to vesting (in shares) | Ìý | 40,000 | Ìý | Ìý | Ìý | 
| Common stock issued for equity raise, net of underwriter costs | 16,044,879 | $ 2,415 | 16,042,464 | Ìý | Ìý | 
| Common stock issued in equity raise, net of underwriter costs (in shares) | Ìý | 2,415,000 | Ìý | Ìý | Ìý | 
| Other offerings costs | (51,282) | Ìý | (51,282) | Ìý | Ìý | 
| Beneficial conversion feature on convertible debt | 1,692,309 | Ìý | 1,692,309 | Ìý | Ìý | 
| Common stock short swing reclamation | 5,433 | Ìý | 5,433 | Ìý | Ìý | 
| Net loss | (2,281,052) | Ìý | Ìý | Ìý | (2,281,052) | 
| Ending balance at Jan. 31, 2020 | 41,679,388 | $ 21,727 | 88,772,128 | (70,000) | (47,044,467) | 
| Ending balance (in shares) at Jan. 31, 2020 | Ìý | 21,727,075 | Ìý | Ìý | Ìý | 
| Beginning balance at Apr. 30, 2020 | 41,747,957 | $ 21,771 | 89,505,216 | (70,000) | (47,709,030) | 
| Beginning balance (in shares) at Apr. 30, 2020 | Ìý | 21,770,520 | Ìý | Ìý | Ìý | 
| Increase (Decrease) in Stockholders' Equity [Roll Forward] | Ìý | Ìý | Ìý | Ìý | Ìý | 
| Stock-based compensation | 3,019,828 | Ìý | 3,019,828 | Ìý | Ìý | 
| Common stock issued for cashless stock options exercised | 0 | $ 22 | (22) | Ìý | Ìý | 
| Common stock issued for cashless stock options exercised (in shares) | Ìý | 22,339 | Ìý | Ìý | Ìý | 
| Common stock issued for conversion of Convertible Notes | 10,000,000 | $ 1,399 | 9,998,601 | Ìý | Ìý | 
| Common stock issued for conversion of Convertible Notes (in shares) | Ìý | 1,398,602 | Ìý | Ìý | Ìý | 
| Common stock issued for stock options exercised for cash | 2,578,700 | $ 1,365 | 4,394,749 | (1,817,414) | Ìý | 
| Common stock issued for stock options exercised for cash (in shares) | Ìý | 1,364,721 | Ìý | Ìý | Ìý | 
| Common stock issued for vested restricted stock units | 0 | $ 206 | (206) | Ìý | Ìý | 
| Common stock issued for vested restricted stock units (in shares) | Ìý | 206,109 | Ìý | Ìý | Ìý | 
| Common stock issued for warrants exercised for cash | 1,081,792 | $ 192 | 1,081,600 | Ìý | Ìý | 
| Common stock issued for warrants exercised for cash (in shares) | Ìý | 192,049 | Ìý | Ìý | Ìý | 
| Common stock issued for services | 19,900 | $ 2 | 19,898 | Ìý | Ìý | 
| Common stock issued for services (in shares) | Ìý | 2,000 | Ìý | Ìý | Ìý | 
| Modification charge for warrants exercised | 25,966 | Ìý | 25,966 | Ìý | Ìý | 
| Amortization of warrant based cost | 27,375 | Ìý | 27,375 | Ìý | Ìý | 
| Cancellation of treasury stock | 0 | $ (17) | (69,983) | 70,000 | Ìý | 
| Cancellation of Treasury Stock (in shares) | Ìý | (16,667) | Ìý | Ìý | Ìý | 
| Net loss | (8,128,987) | Ìý | Ìý | Ìý | (8,128,987) | 
| Ending balance at Jan. 31, 2021 | 50,372,531 | $ 24,940 | 108,003,022 | (1,817,414) | (55,838,017) | 
| Ending balance (in shares) at Jan. 31, 2021 | Ìý | 24,939,673 | Ìý | Ìý | Ìý | 
| Beginning balance at Oct. 31, 2020 | 52,094,217 | $ 24,417 | 105,092,551 | 0 | (53,022,751) | 
| Beginning balance (in shares) at Oct. 31, 2020 | Ìý | 24,416,539 | Ìý | Ìý | Ìý | 
| Increase (Decrease) in Stockholders' Equity [Roll Forward] | Ìý | Ìý | Ìý | Ìý | Ìý | 
| Stock-based compensation | 701,170 | Ìý | 701,170 | Ìý | Ìý | 
| Common stock issued for stock options exercised for cash | 363,385 | $ 447 | 2,180,352 | (1,817,414) | Ìý | 
| Common stock issued for stock options exercised for cash (in shares) | Ìý | 447,134 | Ìý | Ìý | Ìý | 
| Common stock issued for vested restricted stock units | 0 | $ 74 | (74) | Ìý | Ìý | 
| Common stock issued for vested restricted stock units (in shares) | Ìý | 74,000 | Ìý | Ìý | Ìý | 
| Common stock issued for services | 19,900 | $ 2 | 19,898 | Ìý | Ìý | 
| Common stock issued for services (in shares) | Ìý | 2,000 | Ìý | Ìý | Ìý | 
| Amortization of warrant based cost | 9,125 | Ìý | 9,125 | Ìý | Ìý | 
| Net loss | (2,815,266) | Ìý | Ìý | Ìý | (2,815,266) | 
| Ending balance at Jan. 31, 2021 | $ 50,372,531 | $ 24,940 | $ 108,003,022 | $ (1,817,414) | $ (55,838,017) | 
| Ending balance (in shares) at Jan. 31, 2021 | Ìý | 24,939,673 | Ìý | Ìý | Ìý |