help!

I posted a few days ago but couldn't get a good picture but now I can. This is been here for a few days now it just itches a lot. And pretty dry. It's under my boob. My other boob is fine. I've never had this before and I'm not very big so it's not touching my stomach or anything. I also take my bra off at night or like today I'm home all day so I haven't had one on. I've been putting lotion on it and tried auqafore(however you spell it) I try to avoid scratching it but it's been itchy all day.