I'm not gonna pussy foot around it.
Cancer can be cured if caught early. Blood coming out of your lungs is a sign of cancer -- not proof of cancer, but cancer can cause you to cough up blood.
Go catch it. Don't be an idiot and wait for it to kill you.
It is most likely
not cancer. It is probably a nose bleed caused by dry air. But treat it as if it where what it could be, and you aren't harmed.