It shouldn't happen. Let's get that guilt trip out of the way early. Sunscreen, shade, layers - we all know the drill. Even the most diligent among us can miss a spot. The pride of ego thinking you can get your own back. I am ashamed to say it happened to me. I made it stop hurting immediately (and healed it overnight) with a trick I found years ago in the early days of Pinterest. It's natural and basically made from stuff in your kitchen. I don't understand how it works. Maybe something about neutralizing the burn? Plus the coconut oil which is an anti-fungal, antibacterial aka basically nature's Neosporin? I don't know. I just know it works.

So head to the pantry and feel better soon!

white vinegar (really any vinegar but white doesn't stain fabric and it's cheap)
large bowl or mason jar
coconut oil

Mix one part vinegar to 10 parts water in the jar. Soak the washcloth and dab on the burn. For large areas you can up the recipe to make a vinegar bath, the same ratio just way more of both. Appreciate the instant relief of the burning and stinging. Let air dry, then apply a generous layer of coconut oil. Trust me and don't skip this step, you'll feel better after the vinegar but it doesn't last without the oil.

PROTIP: Coconut also does an awesome job of covering the vinegar smell - more beachy, less pickle.