sound button is not working

The volume down button on my iPod Nano (6th generation) is not working. I've only had the product for 18 months and have had no other problems, but this week I noticed the volume buttom was being a bit tempermental. However, the volume 'down' button (i.e. the one which makes it quieter) is not working at all. The other one is, but because it's stuck on the highest volume, I can't decrease it. Is there a reason for this, i.e. is the button broken or stuck? Anyone got any solutions? I know I can go into settings and change the volume through there but that's a hassle. Thanks guys.