when i lick or nibble on my boyfriends ears, neck and nipples he says it tickles and he dosent like it. Does anyone have any suggestion on how to do it where it wouldnt tickle?

also, he made a comment to me the other day, that he had a "bad experience" with his last girlfriend and teeth lol i didnt ask for him to elaborate. I havent decided if i should shy away from slight teeth activies or show him how its done. Cause he seems squirmy about the subject. Yall have any thoughts?