If you have burns all the way around, you should go see someone. It could cut off blood flow if the swelling is too much.
If the blistering is only on the bottoms of your feet then you may be able to avoid a trip to the hospital, but will want to go get (or have someone get) some aloe vera/lidocaine spray. I got really bad burns one year and had to apply that spray almost hourly for the first day or two. I was nauseous from the sun poisoning and couldn’t sleep for more than 15 minutes at a time that night.
Vitamin E capsules can work too if you cut them open and apply the juice, but the spray is best since you don’t actually have to rub it on the burns.