Welcome at HCM.
It looks from your details that it can be either a cyst
(like sebaceous cyst) or this can be a swelling due to abscess
You should also have check up & blood investigations to rule out diabetes
or raised blood sugar problem.Recurrent infection can also be there due to methicillin resistant type of staphylococci bacteria.Please get yourself checked for that.
Hope this all will help you.
With best wishes.