hello I have a small pea sized lump under left armpit.  It is a little tender, feels  kind of like a bruise.  I have had this for a couple of weeks.  I recently had melanoma removed from my back and had a pet scan about a month ago.  I was told I was all clear.  However, I am nervous  with this lump
Welcome to Chat Doctor. 1. The sore lump in and around the armpit / under arm are hair follicle infection / inflammation.2. Thing you should not do is to scratch the area / press the lump / dust rub in any way - as you will complicate and delay the healing process.3. You need to clean the area twice during the bath, and clean the area with antiseptic liquid.4. The other possibilities are enlarged lymph nodes, which also present in that way. They develop in case of any infection / inflammation / malignancy anywhere in the body.  5. In both cases you will need to get a course of antibiotics and painkillers with local hygiene. Good luck. Hope I have answered your query,anything to ask ? Do not hesitate to ask.http://doctor.ChatDoctor .com/doctors/ Chat Doctor. 