I've been vaping a week now and have started getting blood in my nasal mucous as well. I would get this as well from smoking if I french inhaled regularly. Pluss the air is so dry this time of year...

Bloody mucus might give an opportunity for bacteria to grow. I'm not going to worry about it too much unless my snot turns yellow which would be a sign of a sinus infection. Sinus infections can quickly turn into meningitis.