Nosebleeds are typically caused by nothing serious and are usually caused by the tiny blood vessels in our noses cracking due to dry air or an injury to the nose.
If it's due to an injury or dry air the nosebleed should stop after a few hours or a day.
You can apply some petroleum jelly to the nostrils to help keep the nose moist and prevent the nosebleeds from occurring.
If you continue to have nosebleeds and it's not due to dry air then I would recommend seeing a doctor because it could be something more serious causing the nosebleed.
The nosebleeds could be caused by some infection in the nostrils or even in rare cases cancer of the nasal cavity.
So if you have too many frequent nosebleeds that won't stop go see a doctor about it just to be sure.