Last night I went to bed at around 10 o'clock. At about 2 in the morning my dog woke me up and I noticed pain in my left breast. I reached over and felt a small lump that had not been there when I had gone to bed. I looked in the mirror and noticed that it looked slightly swollen and it felt warm. It is right underneath of the lower part of the nipple. There is no discoloration or indentation, only slight swelling. During the course of the day the pain did not go away and the lump has gotten bigger. Is it a cyst? Or something worse? I am 17.