I have a small 'lump' on my right armpit, it looks swollen and reddish, it feels really hurt to me. I don't know it's normal or not, but it sometimes appear 2 or maybe 3 month, sometimes on the left, sometimes right. I thought it could be related to period (?), but it also happens in no period time. I've been ignored it as it's naturally 'cured' or gone within a week, but I'm curious now why and how.