Huh, haven't heard of that before, this sounds like some sort of GameMaker issue / relatively specific to your machine issue where the game got insta minimized which in turned messed with the mouse calibration.
This shouldn't be a problem in the next version, but for now you might need to access settings.ini, which is located in "C:\Users\XXX\AppData\Local\BE_Witches", where XXX is your username.
You should see mouseYCalibration and mouseXCalibration in there, I assume they might have some ridiculous number associated with them, try setting these to 0 then launch the game again!
If the cursor drifts a bit after that, try to access the in game settings (inventory > settings) change anything then hit apply to force the game to recalibrate the mouse again.
Sorry about that...!