Nervous

A few days ago I noticed a red (not itchy and painless) spot under my boob. I immediately felt for lumps on each breast, everything came out good. This morning I checked on it and there is now what looks like a small scratch? The line of skin is sore, not the boob itself. Looked it up, seems like it could essentially be a yeast infection which is common for bigger breasted women (38DDD and never experienced this) but one of the main symptoms is it being itchy. Mine is not itchy.

Anyone have any suggestions as to what it could be? I have terrible insurance so I'm trying to avoid doctors unless I have to.