Several approaches, assuming there is not a walk through walls item, state for the game (some cutscenes might) or debug mode.
1) You make a cheat to shuffle you however many places forward. Anybody that has ever "fallen through the world" (which I am guessing is most of us that ever played a 3d game) will likely be able to attest that most things only care about the immediate collision and if you make it past that then yeah. Find what stores your character's location (might be a virtual one, might be simply what is in the OAM, virtual tending to be if the screen scrolls where OAM is more for "single screen" affairs but not always and https://docs.google.com/document/d/1iNSQIyNpVGHeak6isbP6AHdHD50gs8MNXF1GCf08efg/pub?embedded=true
also has much to say here) and go from there, do note that some games will instead move the world around you. Often a bit clunky but simple enough to do an add 2 to given axis type cheat, or several for different combos or able to be fired in emulator.
2) You edit the map itself to have what is collision and what is not. Can be easier if the game does the whole hidden passage but looks normal thing.
3) You mess with the collision physics itself. As with 1) then you find what controls the location on screen (don't do collisions here, just walk backwards and forwards with nothing else happening in the game if you can - no enemies, no npcs, no animated backgrounds..., not fatal if there are but less changes makes life easier). I would probably go from the button presses there to see how one of those starts out and goes from there. Somewhere in that will be a collision detection. You might however be able to skip a few steps, or work backwards from the thing that tweaks the location value in memory.