I have been biting down on my tongue until its numb. Will this cause permanent damage? It can be numb and red for days after?

Tongue biting. This is not a good habit. You could be damaging the nerves if it is feeling numb. Also you are dramatically increasing the chances of developing oral cancer by doing this.
Doubtful. Discomfort and numbness are normal after biting the tongue and / or certain ENT surgical procedures where prolonged pressure is kept on the tongue while working on other parts of the mouth. Afterward, swelling and numbness are common. This typically resolves in a few days to a few weeks. No medical treatment is necessary. Not to get sidetracked, but i wonder why you are biting your tongue.