Are there any stuff made from iron around? Iron also smells like blood.

It is also possible that you got a nosebleed, but it was not too severe so the blood didn't go out through your nose. But be careful, it may be a sign of future illness. It's hard to tell because there are so many reasons for this. I agree with bpcyclist, don't worry about it too much unless there are other awful signs or symptoms. It has happened on me sometimes, and thankfully I'm still healthy up until now. Though I get actual nosebleed a few days later sometimes.