Viral infections generally subside in 3- 5days.
Since your son is already improving, don't worry just continue with curd and lots of fluids like coconut water, homemade lemonade , chaach ( avoid juices).
Keep a watch for fever , mucus in stools and appetite.
You can give probiotics like enterogermina for 2-3 days.
Next Steps
if your child doesn't improve in next 2 days you can consult a doctor .