Hello,
It can be a result of local muscle injury, infection or inflammation like Pectorallis muscle. This muscle runs is the chest muscle that runs along the underneath rib area. If you work out a lot, especially lifting weights, then it can cause pain. It can be due to pinched nerves or nerve pain due to spinal causes. This can cause a referred pain in the armpits.
I suggest you to apply cold compresses in the armpit and take some anti inflammatory pain killers after prescription from your doctor. Give complete rest to the part and avoid doing any activity like raising your arms or stretching the arms which causes any further damage.
If the symptoms persist then get a MRI scan done from your doctor.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
Hi,
You have not provided enough information for us to be of much help.
Please tell us more about your situation (have you had breast cancer, or any breast surgery, or felt any lumps, etc.) and ask what you would like to know in the form of a question.
Regards,
bluebutterfly