Noticed a weird, new lump on the inside of my cheek a few days ago,
and figured I'd ask someone here about what it might be before I get a
doctors appointment (if necessary).

The "mole" feels completely round, is blackish and red, and doesn't
hurt at all. I can't remember biting myself in the cheek, but I may
have during the night without noticing. I've uploaded a (bad) picture
here: home.online.no/~thallium/images/mole.jpg

Suggestions to what it might be? Cancer seems far fetched, I'm still
in my early twenties, although I do smoke a lot...

Arsenic,

That is one disgusting photograph you've got there. Yikes.

I once had something that looked rather similar that turned out to be
a pyogenic granuloma. More info here:

http://www.bad.org.uk/patients/leaflets/pyogenicgranuloma.asp

If I were you, I'd have this biopsied. Oral cancer is not likely, but
it's a possibility, and you'll want to rule that out.

arsenic,

I urge you to see a Doctor to rule out cancer.  This link might prove helpful:

Mouth Problems
http://familydoctor.org/x2561.xml

~~Cynthia