Any ideas?

Okay, so I had this weird rash looking thing show up OUT OF NOWHERE. On Thursday night, It was the size of a dime, I put hydrocortisone and a bandaid on it. While I was on lunch the next day, I noticed my chest was stinging. It felt like someone was holding an open flame to it. I noticed my chest was turning bright red in front of my eyes. These pictures were taken not even 5 mins apart and you can kinda tell the different in the red.

I do have an appointment tomorrow but I wondered if anyone had any ideas what it could be.

Some things I’ve already been asked and here’s the answers:

Have I been in any weeds? -no, and I have not changed my surroundings (work/home)

Is it from heat? -No, I work inside and I have never had a heat rash before, which days a lot for someone with sensitive skin.

-No I have not busted it open and put bleach on it

-Yes, it is starting to bust open with no drainage, just stinging

-Have I changed soap, shampoo, laundry soap, or anything of the such, no not in over 6 months.

-Does it itch? Yes like crazy.

Have I been stressed? -yes, but I’ve had stress hives before, this feels nothing of the sort.

I just have no idea what’s going on with my body. Any other ideas?