Re: pain in the leg. from the sting. Most important thing is to get the stinger out as quickly as possible. Even after the yellowjacket has left, it will continue to pump venom into you and increase the pain, redness, swelling, etc. Several good poultices available at most drug stores. The Aspirin poultice also works good to reduce pain.
If you have a local surplus store, I would recommend buying a MOPP suit as it too thick for yellowjackets to sting through the suit. (Work gloves and a good head gear are important also, to prevent stings.) It will be hotter to wear, but well worth it. Ask me how I know.
Good luck finding the nest(s). Fire is your friend, especially after dark....
No stinger to remove; that's a bee thing, yellowjackets and hornets don't leave a stinger. OTOH they can sting multiple times where a bee just has one shot.
My leg got bad enough that I went to the doc. He said it was cellulitis (it's not cellulitis) and gave me antibiotics. I asked if I could get an oral steroid (Prednidone) too for the itching and inflammation. He said the prednisone will make it heal slower, and I told him I didn't care if it took an extra couple of days if the itching and swelling and drainage goes away. He gave me the prednisone. I'm taking both to cover all the bases. It looks a lot better (2 inch lesion with well defined edges, it was 4 to 5 inches, weeping, and poorly defined) and doesn't hurt or itch anymore.
I wussed-out and hired an exterminator. I've got at least 3 nests; two of them are huge and I don't know about the 3rd. And there may be a 4th in an old abandoned doghouse, I can't get close enough to check. I try to deal with one and it stirs up the others. I'm getting $6500 from the insurance company to replace the roof, and I didn't think they would cover it. $150 for the exterminator will come out of that; it's cheaper than another trip to the clinic.
MOPP suit? Is that like Tyvek coveralls and a bee hat? (be sure and put boot bands around the cuffs to keep the bastards out) No, 4-letter acronym instead of 3 means it's military. :)