Try rinsing your mouth out with hydrogen peroxide for a few days.
It may be an allergic reaction to an ingredient in toothpaste or mouthwash. This happened to me a few years ago. One day I woke up with a numb tongue. The next day it was very painful. I have red marks on the sides of my tongue, then the middle actually looked like I had licked a hot metal object, felt like it to. I went to my doctor and dentist. Got antibiotics, steroids, and a special mouthwash. I stopped using the toothpaste and mouthwash I was using and switched to an organic one. Now that is all I can use. Doesn't matter what brand of regular toothpaste I use, within hours my tongue starts to go numb.