How do I fix my ipod nano?

My nano is a 3rd generation, works great. I use it with an imac. I just got a thinkpad t420 and hooked my ipod to it, but nothing happened. there was nowhere to eject it, so I was forced to just pull out the cord. All of my music was erased from the ipod (which doesn't matter cause I have it all on my mac and nothing is lost). I know in the manual it says you can't switch the ipod from mac to pc without it erasing your files. My problem is that now when I plug my ipod back into the mac, it won't show up in itunes. and my ipod says "0 KB used, 0 KB free." What does that mean? It charges, but I can't play the games on it, it just turns into the Apple sign. It can't be broken! Please help me fix this, I really don't want to have to pay for apple service or a new one. Please.