Sounds like staph
There are a few kinds of staph infections, a bacterial infection caused by staph aureous a bug that lives on the skin and can recurrently cause boils.
The idea of the nose antibiotic
(i assume your question is "why the nose antibiotic?") is to reduce the amount of staph in your nose where it often camps out. Hibiclens scrubs to your body may also help as does avoiding shaving in groin.