I am not a doctor and if it does get worse you should talk to one.

That said, I usually get a rash a day or two after a Covid vaccination. It’s happened almost every time I get one. I’ve had welts on my forehead and up and down my legs. I have asked my doctor about it because I was very concerned at first. He said as long as it doesn’t happen within 4 hours and I do not have any breathing issues, it’s not a problem. I do have very sensitive skin and break out into hives with a lot of things like fragrances and certain fabrics.