Solo, the same thing happened to me about a month ago, but on my arm. When it started spreading I got nervous, and then when it started to branch out I went to the doctor. The first round of antibiotics didn't work very well, so they had to put me on something a little stronger, and that cleared it up...although there is still a small red bump at the sting site.

I work at an infectious disease research facility, and I'm mad at myself for not visiting my colleagues in the bacterial diseases group, it would have been cool to find out exactly what infected me...I know, I’m such a nerd

Please keep an eye on your infection, I wish you better luck than I had with the antibiotics!