Strange rash appearing on my leg

So, about a week ago, I felt this weird sensation—it wasn't exactly "pain," if that makes sense, but more like this intense discomfort that honestly made me feel pretty unsteady on my feet. When I finally took a good look at where it was happening, I noticed these three strange, circular bumps. I’ve been keeping a close eye on them over the last few days, but they’re super inconsistent; sometimes they shrink down, other times they swell up, and the texture shifts between being hard and feeling soft.

I’m definitely planning on heading to the doctor to get this checked out, but I figured I’d pick your brains here first. Has anyone dealt with something similar, or does anyone have any idea what might be going on?

Just for context, I noticed this right in the middle of the muscle known as the tibialis anterior (http://en.wikipedia.org/wiki/Tibialis_anterior).