Thanks for your query.Based on the facts that you have posted it appears that your has developed what is called as Chronic Fissure in Anus. This is the result of hard stools
.Please give him some stool softener
medicine like Isabgol granules or Cremaffin
available over the counter.
Ensure to give him plenty of water.
Give him leafy vegetables and roughage in his diet to soften the stools
This should help in relieving constipation
which is the cause of this fissure.
His fissure will heal gradually and may take long time.