Hall of Infinite Doors

Your assumption was correct. This door is infact locked by a sturdy iron lock. The lock could be opened by a key, but you do not have a key with which to open this lock. This puts you at a disadvantage. You still have a number of options though. You may attempt to bypass the lock and enter the door, a task which may prove trivial or challenging, or you may depart from this detour and return to the Hall of Infinite Doors.

As always, the choice is yours, but in a universe of nigh infinity the irony is that the decision has already been made in eons passed.