What kind of medical professional should I see for this apparent infection?

There’s a spot on my arm that showed up two days ago. It was there when I got up and got my attention as mild but noticeable pain with slight pressure. I was not aware of how I acquired it.

There’s a firm lump about ½ inch in diameter, not too thick, and a solid red spot like a scab on top, sort of like a little volcano. The area around it is pink and getting pinker. It’s tender to the touch, more sensitive now than it was at first.

I’ve never had anything like this before but wonder if it’s some sort of bug bite.

I can’t see going to a hospital or even a doctor for this, but I don’t know who to see. Doesn’t seem like a matter for urgent care, but it’s also a little scary because it appears to be infected.

Whether we like it or not, we have to venture some kind of self-diagnosis before we can look for help.

So—my question is not “What is this tender pink lump?” It’s “What kind of treatment should I look for, “What kind of healthcare person should I consult?”

I’ve already tried my health insurance’s nurse hotline and couldn’t break through the busy signal. The online chat just linked me to articles and said to call the nurse hotline. It’s Saturday, so my doctor’s clinic is closed.