I am 20, 5'3" and weigh 98 pounds. I haven't had any medical problems in the past. But I am wanting to know what the reason is that I have a brownish spot, the size of a quarter on the right nipple. It's sore, firm, and I noticed it after I started my period. This is the first time I had it and I think it is a bruise or maybe it could be a hicky?