My 5 year old just woke up with a nose bleed. There was a lot of bright red blood and one long piece of dark blood. The bleed has stopped after 15 min?

Observation. If the bleeding is not frequent and can be stopped within a few minutes with pinching nose and holding head back, it may just be a result of dryness, allergic changes, or avid nose picking ! If you are concerned, see your Pediatrician before running to the ENT doc, answers are usually simpler than you imagine, if bleeding continues or child looks pale, go to the ER or urgent care for more help.
Nosebleed. Should not blow nose for 5-7 days. Cut finger nails short. if persists, need to see pediatrician or ENT to check for infection, foreign body, etc.