Well, you might want to visit a doctor.He'll cut it into a certain way and the cracks will be gone when it grows.
My Son Has Bad Cracked And Brittle Toe Nails. They Crack Down The Nails Not Across. They Keep Cracking And Get Caught In His Sox. What Could Be Wrong And What Can I Do About It?
It sounds as if he is not getting the right vitamins and minerals. See your doctor as it could cause all sorts of other problems in the future.