Welcome to healthcare magic!
This problem is fairly common and it is intensely painful and most of the morbidity related to it's location.
The main cause behind the recurrence is the arm pit may be very hairy and sweating, due to overweight
there might be a rubbing of surfaces all the time you move around, or you may be having raised blood sugar due to diabetes
The problem recurs again and again due to recurrent infection in the axilla
, and the contributory factors I have already narrated need to be removed.
For the present problem you need to consult your physician who would know the effective antibiotics and would probably drain the pus under local anesthesia
if it's there.
I hope this advise would be helpful for you.
Still if you have any queries or doubts, please write me back,
I would be happy to solve them.
Wish you a great health!