Conversation: The conversation between human and AI assistant.
[|Human|] I am having an occasional shooting pain at the back of my left armpit three inches below the beginning of the upper arm (about even with nipple).  It hurts when I rub the skin of my armpit with my arm and seems to be in the skin, not the underlying tissue.  There is also a slight numbness in the same area.
[|AI|]  Armpit or underarm pain can be caused by a number of things that include pinched nerve, pregnancy, cancer, swollen armpits and lymph nodes, muscle twitch, breastfeeding, waxing, cystic pimple, cancer, among other causes. But in your case there may be-Brachial plexus nerve injuries - Shooting pain Pinched nerves especially brachial plexus from stretching, pressure or trauma can lead to this problem. This is often accompanied by numbness and tingling feeling and pain that resemble electric pulses.  But exact diagnosis is made on basis of investigation or examination.