Your history certaily points towards an injury
to the Lingual nerve
by a needle, which could have happened during the extraction procedure, which is not uncommon in extractions of teeth in the lower jaw. You see, for anesthetising a localised area for Dental extractions, LA (local anesthatic) solution, is infiltrated around the nerve supplying that particular area. Now, the Inferior Alveolar Nerve
, & the Lingual Nerve, which infact both needed to be anesthetised in you case, lie to close together in the area where they can be accessed to be anesthetised by a syringe's needle, and since the area is quite small, your Lingual Nerve might have been nicked by the needle...
Usually, no treatement is required, as the body is nomally able the repair such damages by itself, however, hot fomentation and a short course of vitamin B-complex (particularly vit. B6) should help... If not then steroid
therepy may be required, for which you shoul consult your Physician.