Very recent research reveals Ultraviolet rays set off a cascade of cellular events that continue to damage tissue for 2 to 3 hours after exposure! You got a burn and you continue to "cook" for hours. Oops! What to do ?? Well, the official recommendations are't out yet but here is what I would do. Cool the skin with cool packs. I like the flexible cool packs that stay flexible when left in the freezer.
Next, take an aspirin for its anti inflammatory effect.
Next, take the plant extract polypodium leucotomos. The trade name is Heliocare. This is a capsule containing a potent antioxidant. You can purchase it in the office or at drugstores. You may need to ask as it isn't usually on display. You can also get it on line so you'll have it on hand to take after a long day in the sun, (even if you don't burn).