Fissures feel like there are razor blades or shards of glass moving around inside when you try to have a BM. Buy a sitz bath (a plastic basin shaped like a toilet seat) for your son. They are available at drugstores or Amazon for approximately $14. It fits on top of any toilet (make sure the toilet lid is up). Fill the sitz bath with very warm water, or hot water if it can be tolerated. Sit in the water until it cools. The warm water will increase blood flow to the tissues in that area and encourage healing on the inside where the cuts are. The warm water is very soothing. Also try a very gentle cream such as Zincofax that is made for babies' bums. It doesn't have menthol so it won't cause further burning sensation the way Calmoseptine can when applied to broken, raw skin. Good luck to your son.