I have a numb tongue from waking up after surgery. It's all gone but one spot what could have happened?

How Long ago was it? It is not uncommon to give local injections in oral surgeries or give topical local to make the intubation less uncomfortable. The local from that could last a while. Also, you could have had compression of your tongue that caused nerve injury. That can take longer to come back. Let your anesthesiologist know.
Possibilities... It's best to speak with, and be examined by, your surgeon and/or anesthesiologist. If your anesthesia required the placement of an oral airway, an lma (a kind of airway), or an et (tracheal breathing tube) then pressure on your tongue may have occurred as part of the normal course of the procedure. Such numbness rarely lasts long so a consult now is in order.