Had tooth extraction/bone graft 3 months ago.have had bitter taste in mouth since.dr says area is healed/no infection. why still having bitter taste?

Could be other cause: The bitter taste could be related to other causes such as sinus issues and related post nasal drip or stuff on the tongue. Would suggest using a saline nasal spray to help break up any post naal drip and brush your tongue to eliminate any trapped food particles. if you dont see improvement in a week recommend followup with an ENT to rule out sinus issues.