Potentially immediately.
It really varies, but if someone sustains a head injury, ideally they would be evaluated by a medical doctor as soon as possible.
Suspected head injuries should ideally not move or be moved in case of cervical/neck/spinal injury.
Head injuries are VERY serious.
Please treat the situation as such.
When I was bouncing, one of my guys killed a guy who rushed the door. He ran straight at a very big, capable man. He was pushed backwards back into the parking lot. The officer pushed him HARD, and the guy was super drunk and limp. He hit the back of his head when he fell from the shove.
He was DOA.
That officer was charged with manslaughter. He is still in prison…
I don’t suppose you could share some more details, to help others give appropriate advice.
You can always call an ambulance and have a person decline treatment. That at least gets them looked at by a paramedic.
Intracranial bleeding, or brain swelling need to be ruled out.
Any physical trauma should be treated.