RAW: The spell creates an object. The object is mobile, but it does fill the space it occupies, just as a wall, cart or other large object would.It is not a creature. Only creatures can squeeze using the PHB rules. Thus, it can't be moved into spaces too small for it. Just as it would not be possible to push a large cart down a narrow hallway, under RAW, you can't move a Bigby's hand down a narrow hallway that is not wide enough to accommodate it.
All of this depends upon a few things. First, it is described as large, but large meaning 10' by 10' is a CREATURE designation. Large, here may, be more subjective as the hand is not a creature. This is going to be up to you and the DM.
Further, a lot of DMs would allow the caster to control the hand in more precise ways. I would. Thus, I would allow the caster to make the hand go flat to go down the hallway. However, this is my RAF (rules as fun) interpretation, not RAW.
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