My 4 year old hit the 2 year old in the head with a toy broom. No one saw it happen. It was right behind the ear. He cried for a long time. Eventually he calmed down but only when lying down. He calmed down watching a movie, holding an ice pack on his head. At one point he even said, 'My ear is done hurting, Daddy," and took the ice pack off. Then he tried to sit up and immediately grabbed the back of his head and laid back down. I asked him to sit up again a few minutes later. Again, as soon as he was 1/2 erect he started to cry. Is this a simple concussion symptom?