I am not sure of any actual treatments. A flea bite shouldn't leave much of a sore. It will probably just leave a small itchy bite that should stop itching within a short amount of time, and as soon as you know it the bite will be gone.
Clean affected area with rubbing alcohol, wash area with antiseptic soap, apply a cold pack to reduce swelling, apply 1% hydrocortisone cream (which helps reduce inflammation. If the flea bite worsens go see a physician.