I have this thing on my arm.it came last summer and my doctor told me its bacterial infection.i used bactroban (mupirocin) on it.it fades but comes back randomly.

Could be MRSA: Methicillin-resistant Staph aureus (MRSA) is a type of bacteria that can cause skin lesions that are difficult to get rid of. If the skin lesion gets better with Bactroban but comes back, it may be due to MRSA infection. The appearance of MRSA skin lesions can vary a great deal. Septra DS or Bactrim (sulfamethoxazole and trimethoprim) DS taken by mouth for 10 - 14 days will usually get rid of an MRSA skin infection.