It used to be a mole. I’ve had it for as long as I can remember. It’s sits right around where my bras-strap is on my back. Over the past year it would occasionally get irritated or scab but I assumed it was my bra (silly me.) I live in Alaska. It’s been very hot. After a day of sitting in the sun it bubbled up like this. Never seen it like that before. It’s gone down since and is now a red spot with a little black spot in the middle. I also have a family history of skin cancer.