Thank you for your query on Healthcare Magic.
Is your child is passing hard stools or having constipation?
Constipation may cause lowe abdomen pain due to strong peristaltic movements.
Or if the is passed hard stool there may be a tear in rectal mucosa which causes pain with bleeding some times.
Give plentu of oral fluids.
If there is constipation you can give dietary fiber
rich food like vegetables and fruits.
Oral stool softners like lactulose
may be given to make stool soft and a little bit loose.
But I advise you to meet a doctor for the examination of his abdomen and for treatment advise.
Hope I have answered your query.