Oat meal will help to heal the sun burn skin very well, try this remedy - 

• Put a cup of oatmeal in water bath with warm water and leave for 15 minutes. Soak yourself in it and wipe your skin very gently after bath so as to keep a thin layer of oatmeal on the skin. This remedy will help in relieving the itchiness and soothe the sun burn skin. 
  For more information and home remedies on sunburn you can read this article –
  http://www.home-remedies-for-you.com/remedy/Sunburn.html