Can an unfinished root canal cause a jaw infection? it doesn't hurt, just feels odd when i touch the swollen bone? not sure if it's bone.

Yes: Most definitely. Get some antibiotics if you are suspecting infection.

Yes: Leaving decayed material in the tooth could lead to spread of infection (or new infection, as a root canal would give an open communication to the mouth). If you have having symptoms of pain/swelling in your jaw, i would go see your dentist.

Yes: The root canal must be completed or the infection will continue to cause damage to the surrounding tooth structures.