Ceara, are you talking about the bony protuberance at the back of the skull? Do a search on occipital bone and see if that's what you think it is...
Our dogs all have fairly pronounced occipital protuberances. That and the 'stop'--the section right between the eyes-- are favorite kissy spots around here.
quite as heartwarming as wrapping your lips around a good occipital and giving it all the kissies it deserves!