Staph infection/MRSA

[Kara703]

My 12 year old son came home from school last Wednesday complaining that something had bitten him by his ear.  I looked at it and immediately became concerned about a possible staph infection because of its location.  It is right where the ear piece to his football helmet sits (he has practice or a game 6 days a week and although I lysol his helmet I imagine it is crawling with germs).
I took him to the pediatrician the next morning and he said it was fever blisters but that he would start him on
Bactrim "just in case".  He did not swab the area to test for MRSA.  I kept him home from school on Thursday and Friday because my gut was telling me it was not fever blisters and I didn't want him to go to school and risk spreading staph.
Today is Sunday, he has been on antibiotics for 4 days as well as using antibiotic ointments and covering the area with sterile gauze.  I called my dermatologist on Friday but she cannot get him in for 3 weeks.  What do you recommend I do from here and do i send him to school tomorrow?  
Please answer quickly, I am worried.