What could cause sharp pain in my left armpit that comes and goes?

There are several reasons you might feel sharp pain in your armpit that comes and goes. One possibility is that a nerve in the upper chest or back is being irritated or pinched. Nerve irritation can send sudden, sharp signals that hurt for a short time. Sometimes, a condition called complex regional pain syndrome can occur when a small growth, like a lipoma (a fatty lump), presses on nerves. Even if you do not feel the lump, it might cause brief bursts of pain. Stretching or movement can also put pressure on sensitive areas in that region, leading to temporary sharp pain. Another possibility is that the pain is linked to a general nerve issue without a clear lump or injury. Most of the time, these conditions are not serious, but they can be annoying when they happen. If the pain continues or worsens, you can use a free symptom checker to help identify potential causes before talking to a healthcare provider who can make sure that there isn't an underlying problem that needs treatment.