Dear friend, welcome to HCM. i see that it is persistent. has it increased in size ? is it soft or hard? is it fixed or moves with fingers? any discoloration? can yu post a photo of the lump here on the website, so that I can tell you more confidently? it is better you see a general surgeon to get evaluated. since there are many kinds swellings that can occur in the armpit, an in-person checkup is more useful. I hope to have answered your query satisfactorily. Take care and please keep me informed of your progress. Good Luck ! May I request you to rate your experience here before you close. Thank you.