2) Hereditary hemorrhagic telangiectasia; this is recurrent bleeding from vascular anomalies.
3) Idiopathic causes: About 10% of people with epistaxis have no identifiable causes.
5) Bacterial or viral infection
6) Nasal septal abnormality.
Avoid nose picking as it can dislodge the clot. If you have high blood pressure, that should be controlled. You would need following investigations to ascertain the cause of bleeding (for bleeding disorders);
1) platelet count, 2) bleeding time (BT), 3) prothrombin time (PT), 4) activated partial thromboplastin time (aPTT), 5) thrombin time (TT) 6) peripheral blood smear, 7) platelet aggregation in response to ADP, epinephrine, collagen, and ristocetin; 8) platelet release assays, 9) coagulation factor assays, 10) assessment of factor XIII activity via clot solubility testing 11) Tests of fibrinolysis; measurement of fibrin split products and D-dimer levels.
If you are taking aspirin or any related products, you would need to stop them.
Please feel free for your follow up questions.
I would be happy to assist you further, if you need any more information.