ipod Touch Account Reset with a new user and Ipad 4 account currently used
As long as you signed out of your Apple ID with:

iCloud
iMessage
Facetime
iTunes and App Stores

Or:
wiped the device before you sold it, you have nothing to worry about. The new owner of your old iPod, won't be able to access any of your data.

If you did not wipe the device, nor sign out of your Apple ID, then the best you can do is change your Apple ID password. This will, in effect, sign the new owner out of your Apple ID.
Even with an Apple ID change the new owner will be able to access:

Any non-iCloud email accounts that you haven't since changed the password for.
Any app's data that has already been installed.

So, change your Apple ID password, and other email passwords (i.e. Gmail), and that will prevent him from accessing your data any further. In addition he won't be able to download updates for apps left on the device.