Suggest Treatment For Nosebleed

Hey, I'm 17 years old and for the past year or two, during specific seasons (Allergy season in spring and now apparently in winter) I have been experiencing severe nosebleeds. At worst, they will be almost daily for a week, and sometimes there will be a week or two in between each nosebleed. I've only had a few so far, just starting less than a month ago. Today at work my nose started bleeding out of nowhere (I work as a cashier in a regular environment). It took about 15 minutes to finally stop the bleeding, which seemed to be running like a faucet to me. I honestly didn't know what to do, and was afraid I might end up being taken out in an ambulance if I couldn't stop the blood soon. I'm not sure what's causing this random bleeding, but it's always the SAME nostril... Any ideas?