Taking SCARY out of used bikes, one bike at a time.
This chain pin is about to break or pop. Look how the plate of the link has pulled out from the pin. When lubing your chain, look for any uneven chain links or stiff links. If you pedal the bike backward over three times, you may see or hear an odd sound or pop. This is an excellent way to find those bad links.
To fix you will need a chain tool and some chain parts like an extra pin or quick link. Sometimes this is an excellent time to replace the chain.