I am 26 years old and noticed a hard lump under my left nipple a few days ago. I finished a round of golf and the next day my left nipple and surrounding tissue was puffy, swollen, and tender... almost painful to the touch. The swelling has gone down and so has the pain but I still feel the lump.
What is this? A cyst? It seems unlikely that the pain would go away if it was breast cancer but I don't really know.