See the best thing to correct this stool issue is dietary changes than medication Try to add green leafy vegetables and banana in his diet His toilet habits also should be changed Ask him to pass stool at same time daily so that he gets accoustomed .Tell him the proper position on how to sit on a toilet .Even though he doesn’t feel like going make it a habit to go at same time daily Take more fruits Despite of all this still if constipation persists consult a nearby doctor

Give diet which is rich in fibre(fruits,vegetables and leafy vegetables). Give syrup.Duphalac 10 ml at night for 1 week

Constipation is quite common in this age group.  Probably dietary changes including intake of more liquids and fibres in the diet is needed more than medication . Without consulting a pediatrician u should not start any medication.  Better to visit any clinic if dietary changes doesn't relieve the constipation.