71 Dart Headlight Switch Removal

If I read your problem correctly, the knob and shaft won't pull out to the "headlights on" position? If that's so, the switch is probably junk. I'd start by trying to pull a bit harder and soak the switch as much as you can with a penetrating oil of your choice. If that fails, figure on getting a new switch, correct knob/shaft, and cutting off the existing shaft to get to the nut.