Most time nose is blocked coz od allergies. i keep sniffling hard to try to open it. this causes nose pain .is this dangerous?can it cause nose bleeds

Possible: Have you talked to your doctor about this? Nose pain can be from contact (from swollen turbinate touching the septum), sinus infection, nasal infection etc. If you have allergic rhinitis, you are more likely to get nosebleeds especially if you blow your nose hard and often. Your condition is not life-threatening but troubling. Yet it is usually treatable. Consult your doctor.