iMac cursor stuck - tried 3 mice - same problem

So my cursor is stuck.....if i move my mouse quickly it does jerk around a little bit, but it quickly goes back to its favourite place currently just above the dock at the bottom.

My mouse is a magic mouse. So I plugged in a spare Apple USB mouse....same problem.

I then forced a shutdown and started up the mac again....the problem persists.

I then tried holding down Command + Option + Escape to see if any applications were causing the problem and needed a Force Quit. Seemed to be no problems but I quit everything one by one and then forced shutdown again.

The problem is still there. So I borrowed my girlfriend's mouse just to be super certain... but yes, it's still persisting so I know it's not a mouse issue...it's something else.

Any ideas?

I'd like to try using Team Viewer or suchlike so that I can use my Macbook Pro to access the iMac...but obviously I can't access Team Viewer on the iMac to allow permission. I can't do anything with the iMac at all. Is there any way I can use my MacBook Pro to help me?

Completely stumped....any help appreciated.

Thanks