2003 Ford Ranger Removing the stereo system assembly cover

I just purchased a 2003 Ford Ranger Edge. There is a KNOB (that's what the parts list calls it) that has "slipped" lose and fallen inside the dash. It is located on the driver's side on the dash next to the stereo system. At first I thought it was a cigarette lighter assembly and housing, but when I looked at a diagram of it, it calls it a KNOB. I have no idea what it is for (on the opposing side is a 12V outlet), so it must not be too important, but it leaves a hole in the dash. I felt inside the hole and whatever it is, it's there, but in order to pull it back out, I will need to remove the cover from the stereo system. I don't see any screws or clips. Could you tell me how to remove that cover? THANKS!