My lingual nerve was damaged during wisdom tooth extraction. what can i should to promote the healing process?

Sadly: Paresthesia is a recognized complication. Depending on the level of damage, in not too severe cases, more often than not fortunately, the numbness is transient and resolves in time, sometimes upwards of a year. I would go get periodically checked by your dentist or oral surgeon to check the progress.

Sooner the better: The sooner you do something the better. Steroid therapy and possibly Neurontin (gabapentin) can help.