iPhone security question
From your description, they had the PIN for only the time it took to unlock it, check it was working &amp; hand it to you - a matter of seconds. 

There's nothing else they can do with it unless they also still have your phone.

The PIN itself doesn't provide access to anything other than the phone, has nothing to do with your iCloud account, App Store, iTunes, email... or anything else.

In you post you mention both the PIN &amp; the password. These are two entirely different things. You ought to edit your question to clarify which you actually mean.