When was he hospitalised  and for how long? After hospitalisation baby might have constipation due to reduced hydration and appetite during illness, medicines etc. Plenty of water, high fibre diet, green vegetables, salad, banana, coconut water, papaya. Increase these in your child's diet. Limit milk and milk products. If symptoms persists, consult a pediatrician.

Give fibre rich diet like Kichidi with dal carrot beans , palak rice . Maintain hydration . If don’t pass then give laxopeg sachet 17 g with water

Kindly consult once for discussion