I hurt my back. What kind of doctor do I see?

PCP, ortho, or neuro. In case of emergency, the er. If you have a relationship with a primary care physician, s/he is best. S/he may refer you to an orthopedic or neurosurgeon, if surgery is a possibility.
Start w your Primary. Your primary care doctor is the best place to start. Any referrals would then be coordinated. If you dont have one see a pm&r doctor.