The U.S. government provided three rounds of Economic Impact Payments (stimulus checks) to all resident aliens and U.S. citizens in 2020 and 2021.
If you received the stimulus check, you either appropriately qualified as a resident alien or you filed your taxes incorrectly and should have filed as a nonresident alien.
Any individual qualified as a nonresident alien who received a stimulus check must return the money to the Internal Revenue Service. The IRS published a FAQ for the third stimulus payment, which confirms nonresidents are not eligible to keep/receive the payment. The IRS provides information about how to return the stimulus payment if necessary.
Filing an amended return with Sprintax will cost $70.95, and you can access the software here. If you have never used Sprintax to file a tax return, you will need to create an account first.