I broke the plastic handle of toilet shut off. Can I fix it or do I need a plumber?

Go to Home Depot, buy new valve with plastic handle. Take Phillips screwdriver, unscrew the handle and install it on the old valve. Easy to do. No need to call plumber

Milo

I completely agree with Milo's answer. A simple and easy repair.
Just remember that the nut has a left handed thread.
Good luck,
Tom

Yep I agree with both experts, Thanks.

John

Agreed but I'd look for a non-plastic replacement. Can you tell us why you were turning the handle?