Usually nasal bleeding
in children occurs due to rhinitis
(running nose), nose picking, dry weather which is self limiting and not dangerous. They resolve by forming a clot in the nose. Best home remedy will be to avoid blowing nose, coughing and sneezing
forcefully. Occasional bleeding can be stopped by pinching nostril for 10minutes. Although its not an emergency, since your son's bleeding nose is for 5 days its always better to get a ENT specialist
opinion in person.
Don't worry he will be alright soon. Take care.