What is the cause of dry nose and nosebleed?

Nasal bleeding can occur when the mucous membrane of the nasal cavity is atrophied, dry, or when capillaries are broken by digging and forceful nose-blowing, for example, common atrophic rhinitis and dry rhinitis.
Treatment can be effective in keeping the nasal passages moist with nasal drops etc. Also, increasing the humidity in the ambient air can be effective in relieving nosebleeds.