Thanks for your query.
Is your child having diarrrhea?
If yes maintain hydration by giving oral rehydration solution,coconut water,lemonade,curd,boiled potato,rice porridge.
I will not suggest you not to give any medication of your own.
Sometimes child becomes fussy and do not eat properly.Try to be patient with him.Feed him with other family members.
If it persist get your child evaluated by pediatrician
for proper management.
Wishing your child good health.