As such the symptoms of a head injury can occur immediately or develop slowly over several hours or days which include -
-Changes in size of pupils
-Fluid draining from nose, mouth, or ears
-Swelling at the site of the injury, or scalp wound
-Impaired hearing, smell, taste, or vision
-Low breathing rate or drop in blood pressure
-Restlessness, clumsiness, or lack of coordination
-Slurred speech or blurred vision
-Stiff neck or vomiting
For a mild head injury, no specific treatment may be needed.
If your child begins to play or run immediately after getting a bump on the head, serious injury is unlikely.
However, as with anyone with a head injury, closely watch the child for 24 hours after the incident.
You can give him OTC pain medicine( acetaminophen,) and avoid aspirin, ibuprofen, or other anti-inflammatory medications .
I suggest you to closely watch him for any concerning symptoms over the next 24 hours.
If he is unstable and disoriented and then consult a doctor or visit ER ASAP.
I hope this helps.