Hello i share your concern this cold be infected lymph node or an axillary abscess in my opinion you should take him to a general surgeon for examination and a battery for tests like hemoglobin CBC ESR pus for culture and sensitivity so that causing pathogen or bacteria can be isolated and proper antibiotics can be advised accordingly enlarged infected lymph node could be related to infection or metastasis due to a cancer so you should not ignore this and this has to be treated appropriately For more information you can upload me a complete medical history or a photograph Hope this helps him wishing him a very good health take care