Holden has a staph infection

I noticed a little bug bite looking thing on his inner thigh on Saturday and its progressively gotten worse looking since then. This morning I noticed another small "bug bite" above the original one, so I decided to call his doctor. he looked at it and said he thinks it looks like a staph infection, however, its not a serious case. Its not filled with pus (sorry tmi) or anything and its not causing Holden any trouble. So they started him on antibiotics but Im so worried about it for some reason, I guess I feel like its a 'dirty' thing and I feel so bad that he has it.
Does anyone have any experience with staph infections? How long after antibiotics are started do they usually go away?