Bleeding nose. Get away in a few days?

I have cold for the past two weeks. Whenever I catch cold, it usually lasts this long. My nose gets blocked. And also I have runny nose. Minimal sneezing. Accumulation of a lot of cough in my throat. These are not the issues that bother me. This morning when I woke up, I had a runny nose. So I took my handkerchief and wiped it (the hanky wasn't hard, and I also wiped it softly) but I noticed that there was a red line where I had wiped my nose. I checked in the mirror and I could see very less blood in my left nostril. Right nostril isn't bleeding. I hadn't injured my nose or anything. I don't understand what it is, and I am a little worried about why is that blood there. Is this something severe that I was just overlooking as cold? Or is it normal and I should just ignore it and wait for the cold to get away in a few days?