Nandroid backup makes a snapshot of your phone, exactly as it is at the time that you made it, while Nandroid restore will return it exactly to that state.
Consider two examples:
- you install FroShedYo, install a few apps, get everything set up. Then you decide to try out xtrROM. You make a Nandroid backup, install and set up xtrROM, then decide that you don't like it and want to go back. At that point you can run a Nandroid restore of your phone from the backup of Nonsensikal and, when you restart, your phone will have Nonsensikal, with those few apps, and everything set up - just as you left it when you ran the backup before installing xtrROM.
- you have everything set up on FroShedYo but decide that you want to try to update the keyboard. You run a Nandroid backup first, then install the keyboard - but the keyboard doesn't work, and all of the apps on your phone start to force close. You then Nandroid restore the backup that you made before you installed the keyboard and, when you restart the phone, everything works the way it did before you installed the keyboard, as if you never did so.
That's what Nandroid backup and restore can do. It cannot, however, do a partial restore - bring back two apps, or the settings on only a single app. It simply resets your phone back to the way it was when you ran the backup.
As bobcat suggests, one solution is to Nandroid Backup Nonseniskal as it is now, then restore what you had before. Install Titanium Backup, backup all of your user apps, then Nandroid Restore Nonsensikal, install Titanium there, and then restore what you backed up from your stock ROM. Just be aware that you should not restore any system apps or data, so you will not be able to restore SMS messages or the call logs.
If you want to do those, there is a solution for that as well, using free apps in the market called SMS Backup & Restore and Call Logs Backup & Restore. Again, this would be similar to what I said before - Nandroid restore your old ROM, install Titanium and the two other apps I just mentioned, use all three to backup what they can, the restore Nonsensikal and, again, install all three of those apps and restore what they can.
I hope that wasn't too confusing...