L.B.
If he's teething then give him some Tylenol or something before bed to help with the pain. If you don't like Tylenol try some Baby Orajel or something which has a more immediate effect (or use both one for the immediate response and the other for overnight help).
That said don't use CIO if you know for sure he's in pain. Ignoring him while he is obviously in pain is probably not the best idea. He needs to know you understand and you're there for him. I realize you are tired but I think fixing the pain will solve the sleep issues, assuming that's truly what it is.
Good luck!