I was cutting my lawn today and put tracter into reverse then went to put back into second gear and I got stuck between. Can't move shifter. I tried lubricating what I could see. I have a Craftsman Riding Mower, not sure of year but I would say it is about 10 years old.
Any guidance would be appreciated as my lawnmower sits in the middle of my yard!!

Try rocking the tractor , then shifting again. Sometimes the transmission gears won't align.

Or you could have a stick or something jammed in the linkages.