The size of your nipples is determined by the genes you inherited from your parents. There is no way to prevent them from being the size they are. But why would you consider large nipples unattractive? Perhaps your "friends" are just jealous and immature.
I would invite you to join a discusion on breasts here:
I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forgo their use.
[This message has been edited by Bobolink (edited 12-29-2005).]