MRSA exists harmlessly on people's bodies. It becomes dangerous when there is a severe wound- for example, my grandma got it when she fell down the stairs, shattered her hip and had to have surgery. That was a few years ago, and because they didn't have a special MRSA ward, they had to totally isolate her. ...That hospital could have been cleaner.
Anyway, I'm pretty sure your kid will be fine. Sorry if this post is incomprehensible... I'm told I get hilarious when I'm on sleeping pills.