A complete history and clinical examination is very important for determining the exact cause of your symptoms. Hormonal changes can cause a disproportionate increase in the size of nipples. Did you suffer any trauma? After any trauma there may be collection of blood behind the nipples leading to the formation of a heamatoma.Breast injury, mastits, breast cyst, fibroadenoma, breast cancer are few other possibilities. Get yourself evaluated by a doctor. Do write to me again.
Best luck and regards!