Good evening Mr Dragon.
It goes without saying to make sure the brush spins as it should before you turn it on, did you check this?
It's obvious that something is rubbing, now you need to take it off again and reinstall it and make sure everything is lined up as it should be. Nothing should rub, obviously.
I also suggest running your burn under cold water as soon as you can, but I can't imagine you'd get a very sustainable burn from that.