How did that get there???

Ok, I know this is gross but...... Can someone please tell me how you get a zit the size of a small island under your arm?

I was just taking a shower and noticed a lump in my armpit.... Of course the first thing I thought was "Great, now I have a tumor!" When I got out of the shower to dry off, I did what any one of you would do and poked around a bit... It was then that I discovered I didn't have a tumor!