<s>[INST] I just noticed a pea sized knot under my 4 yr old daughters armpit. its about the size of a pea or a bb. She has not complained of it hurting...i actually noticed it by tickling her. I am very concerned about this...is this something i should be stressing over? [/INST] Hellenist common cause of swelling in armpit in this age group is lymph node enlargement. As you have described it is painless and there is no redness. I would advise you to observe the swelling if it is increasing in size or there is change in color. Most of the time it subsides on its own. Sometimes there may be inflammation and infection in that case it will be red and painful. In case of infection antibiotics may be needed. Regards </s>