What can I do on a burn?

it was with a hot plate on my belly, with the edge of the plate

I'm not going to ask how you got the burn there, but anyways... Considering it's a hot plate, it's probably a first degree burn. Do not run gold water or ice on it, that can cause tissue damage. You should put some form of lotion on it, preferably one that contains aloe (vera). You should put a cool (not cold) compress on it.

STOP and pass this on:
apply as much of the clear part of an egg, the white part. It provides the nutrition the skin needs to grow. It also stops the pain and hydrates the
skin to keep it moisture. The white will not contaminate the wound. It does miracles. I mean miracles, I heard. Next time you burn your finger stick it inside an egg, just to try it.

Pour coconut oil and rub gently.