please help, i need some serious advice?

okay, so i got my belly button pierced, but despite my regular cleaning and taking good care of it, it has gotten very infected and is migrating out. im going to the doctor's office in the morning, but im trying to do this without my mother finding out. im 18, but still on her insurance. she is super religious (and is a nurse so she thinks she knows everything) and she would be extremely saddened/angered with the fact that i got a piercing. so how do i explain to her that im calling off work tomorrow? also, she has my insurance card. would i be able to have the doctor's office just look it up so i don't have to tell my mom that i need it? please. i really don't want her to get hurt by this, and she is very hard-headed.