I went to the dentist and got a filling where they gave me an anesthetic to numb me. it has been almost 3 hours since i received it and i am still numb. should i be worried?

Not Particularly: Some anesthetic brands last longer than others, some for up to 12 hours! Not sure which one your dentist gave you, but a quick call to the office can alleviate your concerns.

Numb: Local anesthetic shave different formulations dependent on the problem and the depth/length of anesthesia required by the practitioner. Call your practitioner who can optimally address your question. In rare circumstance, it's possible that a nerve can be temporarily traumatized.