Hello!  Corgis are definitely very smart and like to boss one around if they feel they can get away with it.  Corgis are also sensitive, positive reinforcement is the way to go.  As far as the nipping the hands, I would use a firm NO, and yelp and then stop play.  Your pup is young and lots of patience and consistency will be needed.  Redirecting to a proper chew toy like you are doing as well.  I definitely would look into training classes for you and your pup.  Would give your pup a cold frozen wash cloth to chew on for teething.  Take lots of videos and pictures, the years fly by!!  We had a blue merle cardi that we got when he was 14 weeks old and lost him when he was 8 1/2 due to auto immune issues, may of 2014.  We have a red and white pem who we rescued when he was 3 and he is now 8, so hard to believe the years went by so fast!!  if you have any other questions I would be glad to help you out.