Hard to be sure, but it sounds like a chipped gear tooth to me.

Sorry to hear about this, especially right here at Christmas.

I wouldn't drive the car at this point, becaue it's apt to make things worse.
Good luck sorting it out, and ...

Hope you can have a merry Christmas in spit of this setback.

 

transmission rebuild...or whole new transmission.

look on the bright side, you get to upgrade to ap2 transmission and be a little faster!!

 

AP1 transmission gearing is perfect for the F20C powerband (at least for my applications). Look into it carefully before putting optimal F22C gearing in a car with an F20C. It IS NOT as good a match as the original gearing, unless you have unusual considerations.