You cannot purchase ringtones from the iTunes Music Store outside the US. You may think you 'purchased 48 ringtones' but you didn't. When purchasing a ringtone, the first time you click Buy you are buying the
song. That's what you did, and that's how you can play the song on the iPod. In the US, you can then select the song in your iTunes library, click the bell icon, make a ringtone, then Buy that ringtone. If you didn't spend money
twice, you didn't buy a ringtone.
For non-DRM protected tracks, you can
make ringtones in iTunes. You can also use GarageBand (if you have a Mac), or various 3rd party software to make ringtones.