Over the last couple of days I've noticed my right armpit has pain a little painful when resting my arm. I've just been in the bath and was about to shave when I thought I would check everything was alright. I've found a under the skin lump about the size of a 5p coin, it's firm and painful to touch. I'm just wondering if anyone has any ideas of what it may be, I don't want to bother my GP if it is just an ingrown hair, but thought I was ask for advice.