My son is 8 years old and his stomch hurts after having strep throat now he want eat?

Have you fed him?: There is likely more information needed to answer your question fully- but on first impression, if your son hasn't eaten anything because of a sore throat caused by strep, this scenario in itself can cause a stomach ache.

Let him eat: It is not uncommon for children with strep throat to experience abdominal pain because of inflammation of peritoneal lymph nodes (on the lining of the bowel). If he is not nauseated by this and is expressing hunger, feed him bland foods or start with liquids to see how well he tolerates it.