My 4 year old son had a bad fall on his bike yesterday and we don't know if he hit his head or not. Since the fall he has been very sleepy and hasn't wanted to do much. He slept for a while and then just wanted to lay on the sofa all day. This is unusual for him. He also had a fever a few hours later that got up to 101.5. Later in the evening his hand started to tremble. He says his whole body hurts. Should we be concerned about a possible concussion or maybe just coincidence and he just happens be ill and the symptoms showed up after the fall.