woah, hold up there. Ok, first of all, if they called you a nerd and upset you, you should tell your parents. Maybe they'll talk to them. Second, If they insult you, roll your eyes and smile (it really annoys bigger kids, believe me) and just tell yourself they are the nerds if they have to go around insulting people. Lastly, you are not a nerd! Your one of the coolest people I've had fortune to meet.
Being the oldest is difficult and they always vent their anger out on the younger ones. (I'm the oldest in my family, I know these things). The best thing to do is to ignore them, act like they're complimenting you, because if they think they aren't getting a kick out of it, they'll move on to some one else.
So Smile!