Help please. Burn on black throat

[Vixen]

I got a beautiful black throat via Facebook earlier but he has a nasty healing I believe thermal burn on the bottom of his tail. He will be going to the vet for a check up this week but in the mean time I require some help with treating this.. I've never had to deal with a burn on a monitor before.. And this one looks pretty bad albeit healing. I'm unsure how it happened or when as I just got him and am very concerned.