l.e.h.
My daughter always had a tendency to severe, prolonged nose bleeds, which sometimes last over an hour. When she was a teenager, she was diagnosed with Ehlers-Danlos syndrome, which can make body tissues susceptible to problems like that. There are other disorders and external causes that can also cause the same symptom, some serious, some not so bad. So, yes, take your grandson to the doctor and tell the doctor that you want to find out what is causing the nose bleeds, whether it is something about his blood or his skin, or something in his environment or diet. And if there are any other unusual facts about him, even if they seem trivial or run in the family, bring those up too. The doctor will need as complete a picture as possible if he is to have a chance of figuing out what's going on.