The best thing you can do for a blistering sunburn is to prevent it. Always use sunscreen. Always protect yourself from the sun. But if you do get one here's what you do.
Let the blister alone. Don't pop it. Don't break it. If it's going to pop or break let it do it on its own. Before it pops you can use over the counter like Solarcaine or creams or sprays to help with the itching and with the burning and with the pain.
Once it does pop you'll want to put some antibacterial ointment on the blister. You don't want any kind of infection to develop and you want to keep it moist.
You can use over the counter pain medications to help with the pain. Clean the area daily with you know soap and warm water.
Avoid the urge to scratch the area. That can just lead to more problems; more infection and it can make things feel worse.
Stay hydrated. A sunburn can dehydrate you. And it can make you feel like you have a headache because of the dehydration. Stay hydrated. Drink water. Drink clear liquids. Avoid coffee or alcohol because they can dehydrate you.
If you do have any signs of infection, any swelling, puss, fever, aches and pains in your muscles and your joints talk to your doctor.