 [ Symptoms ] should i be worried about my20 year old sons nosebleed that took so long to stop  he must have bled for a good 30 minutes it was not until he pulled what looked like a huge blood clot from his nose that it stopped bleeding it looked like a big slug [ Disease ] it would be concerning if a cause is not apparent dry air colds sinus infection nose picking trauma all can cause nose bleeding it would be concerning if this happens frequently or if he is having bruising in other parts of his body without apparent trauma nose bleeds need to be stopped properly and many people do not do it correctly use your search engine for nosebleed or epistaxis management on webmd and you will find the right way