Common cold, sinusitis, ear infection, sensory nerve compression, peripheral neuropathy as in diabetes, inflamed wisdom tooth, impacted wisdom tooth, dental caries, etc can all cause facial numbness and pain. Hemi facial
numbness is also seen in Bell’s palsy,
trigeminal neuralgia where a spasm may cause numbness, or due to acoustic neuroma which is a benign tumor of the eighth cranial nerve.
Maybe the accidental injury aggravated any of the above reasons.