This could be a sign of some neurological damage, perhaps from birth process or from the Hep B vaccine if he were given the first dose at birth. If this is the case, I would urge you to wait on the vaccines to see if the eye resolves itself.
Here are photos of an 18 month oid baby that was damaged from the smallpox vaccine (1958), you can see in the second photo how his eye was turned towards the nose and the asymmetrical mouth.
Before the vaccine:
After the vaccine:
I don't wish to worry you, but I do want people to be fully informed of the potential dangers of vaccination.
Another link from the above article on HiB and Hep B vaccines causing strabismus.