Hi.. Can understand your concern.. As per your complain alteration in taste and numbing of tongue after dental procedure can happen either due to injury to the nerve if a numbing injection is given and it has directly pierced the nerve hence causing injury leading to prolonged numb feeling and altered taste.. Other reason can be that in case of wisdom tooth removal if the roots of the tooth are closely attached to the inferior dental nerve it can lead to injury to the nerve while extraction of tooth.. One reason can also be while surgical extraction of a wisdom tooth if incision is give deeper towards the tongue side gums can lead to injury to the lingual nerve causing the similar symptoms as you have. The purple bruise can be due to injury to the tongue caused either by the dental instrument during the procedure or due to tongue bite by teeth in numb condition when the patient is unable to feel pain while biting the tongue.. In case of nerve injury it can be temporary or permanent.. In temporary injury it is healed and the tongue gets normal in few days.. But a permanent damage can be a lifetime problem.. I would suggest you to consult an oral surgeon and get evaluated for the cause of your symptoms and if needed a neurologist can be consulted. Hope your query is solved.. Thanks and regards.. Dr.Honey Nandwani Arora