Many . Axillar pain maybe related to local structures like sweat glands causing abscesses ( hydradenitis suppurativa). It may be referred pain from the lung ( rule out cancer) maybe enlargement of lymph nodes. Could be from injury to the axillar nerve from crutches. Could be referred pain from the breast. So, get examined.
Foliculitis or lymph. Commonly foliculitis or lynphadenopathy.
What are possible causes of right underarm pain into surrounding area, worse lifting arm out or up, also feels swollen, lump-began yesterday?
Infection. Infection is the most frequent source of this acute onset illness and would strongly recommend you go immediately and be seen by a doctor. Go to an ER if necessary. Hopefully this will not be too severe and perhaps not due to infection, but do not ignore it and make sure you are seen ASAP. Good luck. Read more...