If you have not flash your ROM yet, you can do a hard reset on your phone
Settings --> Backup & Reset --> Uncheck Back up my data + Factory Data Reset. Then Use GNex Toolkit to relock bootloader.
However, if you have flashed your ROM already, then you need to download the Galaxy Nexus Update Checker Apps to find out which version you have, e.g. yakjuux for Canada by Samsung, of which I am trying to make an original copy. If you have a yakju version, you can download from Mark's link above.