Most likely it would show signs of infection. My son is a nurse and he somehow got a MRSA infection on his upper thigh 2 weeks ago. He had been in contact with 2 patients that had the MRSA virus. Can't recall whether he had a sore there before or not.
He told me it swelled up, got very red and had pus in the center. Obviously they put him on strong antibiotics and had him rest and stay off his legs for a few days. After doing that he is fine.
Stay well...JJ....