That's normal. MS's release notes on the build told people to ensure they update their apps too. Only some OS updates can happen in the OS alone, but the biggest leaps are likely to need apps to change how they work with it too - this is one of those updates.
Store's update allows other apps to be updated that don't get picked up at first, so whatever it's doing must be important.
MOST OF ALL - do a full hard reset on your phone (Settings>System>About>Reset My Phone). This update, like most others, can leave users in a halfway state between versions with a bunch of frustrating conflicts. Do the hard reset, with no backup restore; you'll be glad you did.