If it's the little stalk that controls the stereo you can try a bit of WD40 on it and rotate the wheel/press the buttons to see if it frees up. If you have to remove it be careful as where it's attached can be easily broken (yes, I did that and had to glue it back in....I bought another since that hasn't been fitted!). If you take it apart, as I did, be careful with that, too. There's some bits that will fall out and are a tw&t to put back. The good news is that you can get it working again.