Bought a Samsung Tocco lite on o2 pay as you go.?

I have recently bought a Samsung Tocco lite on o2 pay as you go. When I was having a look around applications, suddenly it wanted a PUK Code and I put it in and it worked. My Mobile is already unlocked so I will be able to put any SIM Card if I wanted to. Since I put in the PUK Code, does it mean I can still put a new sim if I wanted to ?