Winter air can be very dry. I had bloody noses for a few weeks and finally went to the doc thinking something terrible was wrong.
He told me to drink more water. I already did that. He said to get a saline solution spray for my nose. I already did that. He said to put a non petroleum jelly on a q-tip and lightly coat the inside of my nose.
That worked. I use Alba Un-Petroleum Multi-Purpose Jelly.