What Causes Painful Reddish Lump On Armpit?
Its an abscess.
Thank you for the query.
Most likely its an abscess. It appears due to infection of the hair follicles. It can be triggered by shaving in this area.
For sure its not a lymph node.
You should consult general surgeon. It might need incision and drainage.
Hope this helps. Feel free to ask further questions.