Be sure its lymph nodes or a sebaceous cyst. If lymph nodes its sure u have any infection in hand, neck, head, face. Toothache may sometimes do a lymph nodes. But as you say its painful too. In my view its must be a sebaceous cyst arising from hair follicles of your amrpit. Azithromycin 500 x 6days. Go for blood sugar test Hot saline water sponge over it. Zerodol -p twice x 4 days ( if very much pain) with rantac.

Need detailed history and evaluation

After antibiotics not going then it can be child hood tuberculosis lymph node Get esr blood test and chest x-ray Nothing to worry it's mild disease most times it goes on its own. Good nutition is key If test abnormal then you may need course of medicine