First of all, I hope you're pretty young, because I can't imagine the kind of adults who would tease someone about a disability. Seems more like something kids would do.
In general, I think you have to evaluate the situation and ask yourself if maybe the person isn't aware that what they're doing is really bothering you? In that case I would say just be direct, say something like, "Could you not keep giving me s**t about my ear? It really sucks." But if you think they're doing it to get a reaction out of you, and they like seeing you uncomfortable, which is sometimes the case if they're the type of person that puts others down to make themselves feel good, talking to them might not help.
A friend of mine used to tease me a lot, I started talking to him less, he emailed me that I was too sensitive. I wrote back, "So? I like being sensitive." And he wrote "I like you being sensitive, too. Sorry." He's pretty careful about that stuff now...of course if you're a boy, that might not work as well...
Another thing I do when someone purposely says something I feel is rude or insulting is to get sarcastic, just say something like, "Thanks, that's exactly what I needed to hear right now." They usually drop it after that...personally, I think it's okay to get pissed off about teasing, it is pretty immature.