Thank you for your query.
It is not unusual to have blood present in stool when a child is having diarrhoea
. From your query it is not clear whether your son is still having diarrohea? In case diarrhoea is persisting then he needs to be taken to the ER so that treatment can be initiated. If his diarrhoea is under control and this blood has been only one instance then you can wait. If further stools contain blood then a detailed examination and investigations are warranted.
I hope I have answered your query to your satisfaction.
Wishing your son all the best.