How bad is it if you repeatedly have blisters on the inside of your mouth from hot food?

I seem to eat food right when I get it, even if it is boiling hot! Then I wind up with some canker-sore or blister right in the inside of my lip, below it, in front of my teeth. It takes a long time for it to heal and by the time it does, I wind up getting an other one, shortly afterwards. I was wondering how much damage it does to your mouth? Thank you.

hurts dont it