Removing knob from front panel?

This is going to sound like a stupid question, but I am having difficulty removing the knob that controls the water level. I need to remove it so I can access the panel to replace a part. The other knob (I believe it is the one for the cycle) popped right off, but this one seems to be spring loaded or something. I have done everything I can think of but I can't loosen the knob. I am hesitant to try to force it. Any advice would be greatly appreciated.