If it is red and swollen or has the appearence of a spider bite, my first concern would be MRSA. There are 2 types Community Acquired or Healthcare Acquired. HA is usaully after receiving treatment, not always.

MRSA escalates RAPIDLY, requiring immeadiate attention. A boil may appear soon. If so demand a culture, it will require lancing. Under no circumstance do you discuss treatment for MRSA without actually viewing the results and having them explained. If that explantion is superfilous ask for a referral to a infectious disease specialist.