VicR,
Not facial nerve damage. Stress and inflammation of the cranial nerve that controls that part of the face. The cranial nerves come out of your neck.
Sounds like maybe the 7th cranial nerve. You may have jammed your neck when you bumped it. Or, a jerking reaction to the hit could have tweaked your neck.
An upper cervical chiropractor or physical therapist might be helpful. The therapy should be very gentle. No neck popping/cracking.
These Are the 12 Cranial Nerves and Their Functions