Cursor is stuck on the upper left side of the screen. M1 chip on an iMac.

Sounds like your Mouse or (Trackpad if applicable) has stopped working or is unpaired.

see > If you can't connect your Magic Keyboard, Magic Mouse, or Magic Trackpad to your Mac - Apple Support

If that support article does not help, then temporally connect your Magic Mouse or an aftermarket USB mouse to the iMac.

Connect the Magic Mouse to the iMac, wait 1 minute, then disconnect the Magic Mouse from the iMac and test.

FWIW, you may have to acquire a USB mouse in order to pair the wireless mouse to your Mac. Any inexpensive one would do.

You're welcome.