Hi and welcome to the forums!
When we first got Millie she was very quiet and well behaved, even when playing! after about a week - 10 days she was barging around all over the house making lots of noise and generally trying to take charge
Give your little one some time, it could be that outside he feels safer and so is a little more adventurous, but inside he hasn't quite gotten used to the environment.
BTW - whats a Chocolate & cream look like? please post some piccies ... or have I missed them ? :?: