The most common reason for children to bleed from one nostril is that the mucous membrane of the nasal vestibule area is eroded due to repeatedly digging the nostril for a long time, and the bleeding blood vessels are exposed outside the eroded mucous membrane, forming bleeding points or bleeding surfaces that are prone to bleeding, and nasal bleeding can occur after light touching or stimulation. The bleeding can be cured by applying Bactrim ointment on the surface and not digging the nostrils again to promote the recovery of the eroded mucosa so that the blood vessels are again under the protection of the mucosa. You can also microwave or laser cauterize repeated bleeding spots to promote healing and stop bleeding.