Maybe the Falcon crashed into something turning it into a squat version of itself. Kinda like how pugs are made by letting normal dogs run into walls.
Seems like more major surgery than Han and Chewie would be able to do. That’s like a major hull reconstruction.
Maybe it takes alot of damage along the way before we see it in ANH?
They would basically have to destroy and rebuild the entire front end of the ship to get it to match.
That's less "a lot of damage" and more "beyond totaled."
YT-series ships are portrayed as being reasonably modular. All it would take is a few straight-through turbolaser hits across the bow to make it cheaper to replace the whole front section than repair it.
Or it may have been a strategic choice having nothing to do with damage. If the Falcon became too recognisable and notorious, a decent nose-job would be a good disguise.
it doesn't matter since it's fake
https://www.bleedingcool.com/2017/12/27/leaked-han-solo-movie-art-fake/
“Leaked” Han Solo Movie Art Is Fake, Says Disney and Lucasfilm

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.