It depends what caused the bloody nose.
Just to make sure, did you experience any trauma or injury to your face or nose?
You can experience a small amount of blood from your nose in cases of seasonal allergie or weather changes, for instance. The small blood vessels in your nose can "burst" if you blow your nose, or if the inside of your nose gets too dry.
Do either of these scenarios sound like what happened?
Please let us know if your nosebleeds are recurring, if the blood was considered a large amount, or if there were any pain involved. These would be reasons to call your doctor, along with any trauma or injury to your nose, face or head.