What do i put on a burn thats cracking?

First thing is to make sure it stays clean. As long as it's not turning red on you (sign of infection), you might try putting a little Neosporin ointment on it. That'll keep it from drying and cracking, and also provide some antibiotic protection. The other poster suggested aloe vera--that is good, but for myself, I'd prefer the antibiotic ointment. If it is infected, then I would suggest you go visit your doc.