My friend if I can make liquor out of flamin hot Cheetos, a bit of burned mash is nothing to worry about! If you ask me what makes a good home brewer is the desire to make something and the ability to do a very large amount of cleaning lol. Besides, you never know, maybe the charred mash might result in some tasty dark Carmelized notes in the beer :) as they say: relax, don’t worry, have a home brew.