Signs and symptoms generally show up soon after the injury. However, you may not know how serious the injury is at first and some symptoms may not show up for hours or days. For example, in the first few minutes the injured person may be confused or a bit dazed, but an hour later they may not remember how he or she got hurt.
It is important to check for signs of concussion right after the injury and to monitor the injured person for a few days after the injury. If the concussion signs or symptoms get worse, you should seek emergency treatment without delay.