Thanks for your query, I have gone through your query. The numbness in the tongue could be secondary to the trauma to the nerve by the tip of the needle while injecting local anesthesia. The trauma would have caused injury to the nerve resulting in neuropraxia resulting in loss of sensation. Nothing to be panic, usually it will reverse back to normal in few days to week. Mean while you can start with nerve regenerating drugs like capsule neurobion, once daily for a month. You should take extra precautions not to injure your tongue when you bite or consume hot and cold things. I hope my answer will help you, take care.