Hi Elliott. A burn usually covers a larger area than just one scale, so your snake could have injured itself some other way. Just to be safe, make sure that your heater and any light source are guarded (so the snake can't touch them) and regulated with a thermostat. Is there anything sharp in the tank that your snake could have caught itself on?
Betadine is fine for reptile skin wounds. I agree with JaneW - your snake will shed more often while it is healing. I think it was coincidence that it shed ten minutes after you put the Betadine on.
Keep monitoring the area where your Corn lost a scale. If the damage spreads, you need to take it to the vet. But as long as it carries on shedding and the area is clean, it should be fine. Most of the time, lost scales grow back, but sometimes they don't.
If you are using bark or aspen substrate, I'd use newspaper instead, just while the Corn is healing. That stops bits and pieces sticking to the wound and reduces the risk of it getting infected.