Why did I develop a rash on my ?

I know this sounds weird, but I have a little rash on one of my . It just appeared yesterday and I noticed it as I was undressing after I came home. I think it might have something to do with the silicone push up pads I was using, because I noticed an almost similar reaction (kind of like slight reddening and a little burning) when I wore them before, though it doesn't happen all the time for some reason. Does anyone know what's the problem??