Armpit rash?

Liz • Mommy to perfect girl Payton 💓

This appeared about 3 days ago and I’m not sure if it’s a heat rash, razor burn or what. Everything I put on it makes it burn. I haven’t been shaving since it appeared but it isn’t going away. Anyone have suggestions as to what I can do to alleviate this? I’d go to an urgent care, but I don’t have money for the copay right now.