I've been getting random nose bleeds just out of no where. The weird thing is, it is always from my left nostral. I think I have been getting nose bleeds while I'm sleeping too but I can't completely confirm it. Today I woke up and I felt a gulp of liquid coming to my throat and from experience I ran to the bathroom because I knew it was a bloody nose. I'm not sure what could be causing this. If it was a dry room, why would it always be from the left nostral? This does not happen daily or anything, maybe once every 3-4 weeks.
Your nose is bleeding from damage to one particular vessel, and that vessel is located in your left nostril. There is no reason for the other side to bleed! Try lubricating the inside of your left nostril with vaseline and it will heal.
Like kitkat77 said, the weak blood vessel is in your left nostril, so that's the one that bleeds. It is not uncommon for extreme dryness or forceful blowing of the nose to cause this. If it is only once every three weeks or so, I wouldn't worry too much. A nosebleed can come from the front of the nose interior (in which case, the vaseline may help with the dryness), or deep within. If it becomes a daily problem, you can get a doctor to cauterize the problem blood vessel.j.
Tell your doctor about your bleeding. Nowadays, it's very easy to solve the problem, for at least several months. Your doctor puts this substance in the nostril that bleeds and it'll help you stop getting nosebleeds. It takes a total for 5 minutes and while it is uncomfortable, I find that it is worth it. For about a year, it helped me with my nosebleeds a lot.