My 2 1/2 yr old fell off a chair hit head on the floor. has a bump on the side of head no vomiting stopped crying she seems fine. should i be alarmed?

Closed Head Injuries: Closed head injuries in children are relatively common due to their activity level and altered center of gravity. Most serious head injuries are associated with loss of consciousness, seizure and immediate vomiting. Serious injuries rarely become apparent within 24-48 hours after the injury and are associated with multiple episodes of vomiting, altered mental status, seizures, etc,