The misinformation in this thread is scary. First off:
1) Abscess: It won't go away on its own. You will need antibiotics. If your dentist suggested salt water for it that means it is reaaaally small. If you feel it's not small then ask for antibiotics, unless you enjoy the pain. Popping the abscess yourself is not that smart when your mouth is full of bacteria IS IT? Yes you will get relief but chances are you are in for worse.
2) Root canal: The RC by itself does not hurt (obviously done under local anesthesia). The reason why it might hurt is in case you get an infection during/after the canal (because blood may enter the root or the root/gum may bleed deep down). The infection causes the pain. Best course of action when you get a root canal is to ask your dentist for an antiobiotics prescription just in case. If the next day you have pain that is getting progressively worse then get the pills (note: you may have slight pain after the RC but it should be getting less and less, not worse. Also, if you bite and have pain when you do that means the filling need filing and you should go to the dentist to sort it out).
If you have a problem that needs a root canal and you ignore it then you will, most definitely and unavoidably, end up extracting the tooth.
As far as I'm aware it's not an abcess, just a slight infection of the root of the tooth.