It does look suspiciously like a bite wound, but it is impossible to tell for sure through a computer screen.
I would recommend bringing the cat to a vet. Is he current on his rabies shot?
If the vet determines it is a bite wound, They can treat him with antibiotics. Those kind of wounds have a tendency to get infected and can cause some pretty serious abscesses to form. The infections can often get so bad that they spread to the underlying bone. It's best to take care of them before it gets to that point.
If the vet determines it is not a bite wound, they will offer you the appropriate treatment options, which may be similar to bite wound treatment.