Headlight switch knob replacement

I'm trying to replace the headlight switch knob on my Dart. I have a nicer one (that somebody already had the stem pulled out of) that I want to use. I've got the original knob with the stem still attached pulled out of the headlight switch. I need to get the stem out of the knob to put it in the other knob. Does anyone know a way of getting the stem out of the knob? I don't know if they were pressed or glued in but I can't get it to budge.