Hello there. Bleeding from nose usually occurs in majorly two conditions if there is any kind of trauma to the nose or internal organs and other reason is high blood pressure when the body chooses the nose as outlet for blood to reduce the pressure otherwise it can cause hemorrhage in the brain. It is most commonly seen in elderly patient who are having high blood pressure. Since you have mentioned your father is a person having high blood pressure and he is not on medication that is a very risky situation. It is your duty to pursue him to take his BP medications regularly otherwise same scenario me follow in the future or if by some chance there is no bleeding then it might cause hemorrhage leading to a stroke and make him paralyse for lifetime. My suggestion would be to get a complete body checkup done and if she is having high blood pressure continuously then he should be started on blood pressure medication.