My son hit his head over the weekend and it gave me a good scare! I was told by the Dr., to be have him seen if he three up 3 times or more. He said three times, because vomiting right after a fall is common, from stress and impact. Vomiting more then 3 times, means there is something wrong. I was also told, to watch for them being very clumsy and irritable. If they are extra irritable, this is a concern. If one pupil is larger then the other, take him in.