Welcome to health care magic!
I have read your question carefully and from my clinical experince I can say that it was a real hard hit and can be a case of concussion
. Please don't panic but do get your son checked by a neurologist
. Had I been treating him, I would surely go for an MRI
Brain to rule out any other injury
to brain tissue.
It will be wise to see the doctor in person and follow his advice.
Hope the answer helps your son in getting alright
feel free to ask more questions.