I have been stung by wasps and bees but never a yellow jacket. I would think it would be similar though.
My bee stings lasted two or three days before they went down (untreated except for hydrocortizone cream) and my wasp sting on the palm of my hand once was four days.
I seem to remember when I was young and got a bunch of bee stings on my back from sliding down a hay stack that they made a paste out of baking soda and put on the stings. It supposedly helps draw any residual venom out of the sting.
I was feeling better by the next day.
Best of luck and keep us informed!