I have some concerns about changes I've been noticing in my breasts. A couple weeks ago, my nipples (mainly my left) starting itching. While the itching has improved, I have noticed a tiny bump on my left nipple that is slightly larger than the others. I am thirteen so this could just be puberty, and it looks as though it might be a pimple because it appears as though there is a white head, but I can't be sure. Could this be a sign of breast cancer?