What exactly do you want to do? You can not 'change' a master file because, well, it is the master...
If you like all the adjustment you did on a picture, you can:
1- duplicate the version and restore the master settings
2- export the version as a JPEG then reimport the JPEG as a master in Aperture but I dont really see the point of doing this...
Masters images as the pristine version of your capture, you should never mess them up. You play with versions.