What is the Timetable for Recovery from Sensory Nerve Damage Due to Chin Implant?

Complications and side effects are very uncommon with chin augmentation of which the most likely side effect is altered sensation in the chin and lower jaw, called neuropraxia, which may be temporary or permanent depending on the extent of the surgery. Typically this resolves within several months to a year. The wierd sypmtoms you described may actually be sign that your nerves are knitting back together. I suspect you will have a full recovery.A plastic surgeon will be able to tell you if you are at particular risk for this type of side effect at time of consultation.

This is likely a neurpraxia and should return in 3-6 months.  Sometimes you will have a "wierd" sensation where it's not numb but not yet normal that can last 12-18 months.  With your description, it seems pretty safe to say that it should return.

The facts that your sensory defect began well after your surgery, was subtotal, and has shown some signs of (incomplete) improvement all suggest that your nerve is not cut, and you can likely expect full recovery over a 1-2 year window.