How can I treat my sun burn?

Topical lidocaine. You can buy a topical aloe gel with Lidocaine that will take the edge off for a little while. The main thing is to moisturize it and wear a broad spectrum sunscreen for uva and uvb of at least spf 30.
Care. Keep sunburn cool with moist cool/cold compresses. Avoid alcohol containing products. Break off pieces of aloe vera plant & apply sap to skin. Consider non-steroidal anti-inflammatory meds to reduce pain. Don’t yank off peeling skin or burst blisters. Seek medical care for severe pain, fever, lack of improvement of symptoms within several days or if a large surface area is blistered.