Hello,
It can be due to sunburns or photodermatitis. Sun burn are due to the excessive exposure of the skin to the dangerous Ultra violet radiation from the sun. This in turn damages the normal structure of the skin tissue. But the body has the defense mechanism of producing melanin, which is a pigment which gives coloration to the skin. Melanin helps in converting this Ultraviolet radiation back to heat which is radiated off the body.
Thats why skin feels hot. The best treatment of sunburn is to avoid exposure to sun. Usually the sun burn will heal to normal in few weeks time. Apply cold compress to relieve the pain and analgesic medication can also be taken. Soothing lotion, Lidocaine or Benzocaine ointments also prove helpful for the pain. Always consult a physician before undertaking any form of treatment.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.