I Have A Large Bumpy Rash In My Left Armpit,

I have a large bumpy rash in my left armpit, and a very small one in my right armpit. I have had these for about two weeks, but the one on left became very painful last night and has remained so. It is worse when my arms are down and there is skin on skin contact, not as bad with a shirt on, which prevents this. My question, is it okay to wait to see my doctor, it usually takes a week or so to get it, or should I go to an instacare where I could be seen today?