I'm an average 22 year old male. I do smoke marijuana often and occasionally I'll mix a small amount of tobacco into it when I smoke it. So last night I smoked from a bong at my friend's house, and when I wiped my lip with a tissue I saw a small blood stain, I did it again and another stain came up. After the third wipe nothing came out. The stains were circular, about 2 mm in diameter (O <= each one was about that size - to scale).
I don't feel any pain in my chest or throat, or a shortness of breath, and this is the first time I have ever coughed up blood. Now I do occasionally cough up bits of marijuana resin in my phlegm so I don't know if it is related or not. My friend told me that sometimes during the Winter months your nose can bleed and it can go into your lungs, but the amount of blood that came up didn't seem enough for a nose bleed. I'm a little worried, I hope I don't have lung cancer, please help.