I'm a 14 yr old girl, and i have tiny little pimple-like bumps on both
nipples, but recently i got this bump on my left nipple, and its about
one third of the size of the nipple itself, no pain, no itchiness.
The bump on your nipple is most likely a small cyst or even an ingrown hair. However, the only way to know for sure is by going to see your doctor. It's best to have any changes to our breasts checked as soon as we notice them, if only to be reassured that everything is fine.
Take good care,