Scary rash???

Kasey
Randomly appeared while sitting here watching tv. Hurts and burns like a SOB! Not sure what I should do about it! I was in the sun today but i applied sunblock and I have redness nowhere else... I'm an RN but I've never seen anything like it appear so rapidly. It's 10pm here so contemplating waiting until tomorrow to see a dr cause I don't think it's worth an ER trip...it almost seems like a chemical burn?? Hasn't spread any further,  o swelling, but it is warm to the touch!