Where is the creak coming from, inside the car or underneath? If inside it will probably be a column bearing, nothing to worry about, otherwise a worn steering joint or rubber bushes, in either case its unlikely to be expensive unless its a fault in the rack itself.

There are many things in the steering and suspension system that it could be.

I would say though, that rule number one is that if it's still under warranty get it in to the dealers and report it. Even if it doesn't get fixed now (intermittent, say) then failure occurs later you have a case because you reported it within the warranty period.