It can be due to trauma or infection.
yes dont do it you'll get a mouth sore too
This is normal for a boy in his early teens and it won't last long. Swelling around a boy's nipples is one of the several changes that come with puberty.See the Related Questions below for "What is puberty?"----
if your guineapig has nipples means it still is a boy.
Boy guinea pigs don't have nipples.
darker nipples
no it is not
Sure he can be.
The best way to deal with an out of control teen boy is to send to military school
Nothing comes out f them.
is a boy
its because when you are a zygote then you can either be a boy or a girl so the nipples develop anyway