Hi
This might be a gastroenteritis- virus being the most common cause.
There are no magical remedies that will stop his stools immediately.
Be sure he drinks well.
You might give him plenty of water,
ORS, vegetable soups, Rice based Porridge, Boiled potato, Banana and plenty of curd.
Avoid cow`s milk and fruit juices for few days as it might cause increase in frequency of stools. You may give him soya milk instead.
You may give him
probiotic sachets- like Econorm- 1/2 sachet twice a day for 5 days.
If he has
vomiting too, you may give him syrup
Domperidone according to his weight.
Be sure he passes urine at least 4 to 5 times in a day.
If he is not drinking anything/ urine frequency is very less/ he is dull and tired/ you see blood in his stools/ he develops high grade fever- do not hesitate to visit the ER.
Hope my answer helps you.
Wish your son a speedy recovery.