3d printer bed not leveling

I don't know why, but the back right 3d printer bed leveling knob won't make the bed go up and down when I twist it. I tried taking the knob off and the screw won't do anything at all either. I know that this is probably just a simple piece of hardware that I need to tighten, but I don't want to make the issue worse or break something by just playing around with it.