Hi, hopefully there is no fever, also you have not mentioned about loose motions. from history it sounds to be start of gastroenteritis, or gastritis, .watch for any loose motions, and if present and start in ORS. Needs to be seen by doctor Disclaimer “This provisional advice provided by me stands subject to the actual examination of report/ image  and is based entirely on inputs provided to me. It should be correlated with clinical findings"

He may be developing gastroenteritis. Look out for loose stools. He will need ORS to replace fluid & electrolytes. If voming is frequent you can see the pediatrician to get him checked & could've medicine to stop vomiting. If there are no loose stools, needs to get his urine tested to rule out Urinary Tract Infection.