Large lump under my left armpit? (recurring)
So a few years ago, spring of 2007, I had this painful lump under my armpit that appeared within 3 days or so. I went to the doctor and was given a shot in the butt to help jump-start my antibiotics, and within a week or two, it was gone. For the past couple years, it was reduced to the size of a pea, didn't hurt at all, but still felt a bit solid.
Just now in the past couple days, it's hurting again and getting bigger, so it came back. Right now it's about the size of half a golf ball.
Any ideas on what this might be? The antibiotics helped last time I had it, but apparently it's a recurring problem. I definitely don't think ingrown hairs can cause this.