Unable to log into 2017 iMac which has a full disc

Hello support community

I've read other threads, but can't find one that covers my situation.

I can get to the log-in page in Safe Mode, but the keyboard doesn't respond & the cursor is frozen, so I'm completely locked out.

If some kind person could help me out, I'd really appreciate it, as I'm 72y/o, & prone to confusion issues brought on by head traumas.

Best wishes

John