Originally Posted by
andrewclaus
From the photo, I'd suspect the small chainring. It looks like the teeth are starting to get the "shark fin" shape, and there may be a burr on the leading edge.
Agree that the small ring is worn or "starting to go." It looks like the OP is spending all their time on the small ring. This is why, when possible, it is better to use the big ring and therefore the bigger cogs on the cassette. More chain ring and cog teeth engaged means much longer life for both the chain rings and cassette.