Your dentist should be tracking the progress you make with your numbness. It can take up to 6 months for your sensation to return. If it doesn't return by then, then the numbness will most likely be permanent.
I'm not familiar with nerve damage with extractions. I don't do wisdom teeth extractions. You might want to ask the oral surgeon in the Oral and Maxillofacial Surgery forum
You should go to an oral surgeon. Personally, I would never let a general dentist remove wisdom teeth. Oral surgeons deal with this procedure all day and therefore have more experience. If your tongue is numb, it indicates that there was damage to the lingual nerve. If it is completely numb, the nerve may have been severed....which should not have happened.