What to do if a wasp stings you on your foot and it swells up?

Ice, benadryl, (diphenhydramine) TDAP. Remove the stinger if present. The sooner the better get ice on the area. Take some Benadryl (diphenhydramine) and ibuprofen, and make sure you get your tetanus booster in the next few days if you're due. If you start getting widespread hives, rash, difficulty breathing, faint - go to ed or call 911 right away. Good luck!
Ice. Apply ice immediately, if you see as tinger remove it gently with tweezers, and take an oral antihistamine like benadryl (diphenhydramine).
Clean the area. Clean the area and apply ice for a few minutes...Then and apply "after bite".Warm compress, etc.