If he has fever or abdominal pain
or both he should be shown to a doctor to rule out appendicitis
. Otherwise give him plain water followed by some semisolid food. If vomiting
stops you need not worry. If he complains of headache he needs to be seen by a doctor asap. Check the color of urine to see if he has jaundice
.. If vomiting persists he has to be seen by a doctor.