Ipod headphone problem

Hello,

I have had my ipod headphones for a while and suddenly the sound isn't coming out right. It comes out of the little hole behind the headphones, not from the part where it usually comes from. I don't know how to fix this, and it has happened before with a different pair of ipod headphones and that's why I got this pair. They have gotten quite expensive, though, so I want to fix it, not buy new ones. If you could help that'd be great. Thanks!