AWKWARD QUESTION ABOUT - Don't read if talking about this makes you awkward.?

Okay, so I woke up this morning and one of my s is really itchy, I don't know why. I am either a D or a DD bra size (I have a D that still fits me, but most of mine are too small so I'm gonna get re-sized) and I'm 17 years old. I googled it and got as many answers as it's exyma to it's cancer O.o I don't have allergies to the shower gel I used cause I've been using it since summer holidays and nothing till now, I wore a new pair of PJ's last night but why only one and not the rest of my skin? It scares me most because it came on so suddenly, I just woke up and was itchy. This never happened before, and when I scratch the spot (The top half of my right and around the nipple) It turns red and has tiny red dots on it, almost like when you get a tiny cut when shaving but these don't bleed they're just tiny and the same colour.