Sometimes when a person gets hit they can have a concussion and it might not show sypmtoms right away, but later on. A licensed health professional could always be consulted. If there are symptoms such as headache, unconsciousness, dizziness, vomiting, vision problems or any new symptoms it might be cause for investigation. A friend of mine had a 2 by 4 hit his head and he lost part of his vision, I think right away or soon afterwards