When should i take my son to doctor after a bump to the head?

Head injury: Worrisome symptoms would be severe headache, nausea or vomiting, unusual drowsiness, confusion, unsteadiness or visual disturbance. If he's sleeping awaken him periodically to assure he is alert and normal for the next 24 hours.

Loss of consciousnes: Any 4yo that is knocked out by a fall should be evaluated. It is common to get a bump, vomit x1, & get a headache.If the kid recalls the event, did not loose consciousness& does not start vomiting repeatedly, you can safely monitor him at home.Let him nap/sleep on a normal schedule & check him out occasionally for signs he vomited in his sleep.Go to the er if something happens that spooks you.

Agree with all : other Doctors. Keep in mind that after 48 hours without neurologic syptoms or findings developing the likelihood of a significant head injury damaging the brain structures is exceedingly low. In other words he should be fine.