Screwed up Fin Box Install? Yes you can fit it!

You'd be better off fixing the toe in angle now so the board surfs correctly. The left fin now will create a lot of drag and the board will always want to pull right...

Simply wobble the fin box out, it will take some foam with it but fill the void with a Q-cell/resin slurry just like a ding repair. You want to make the slurry thick so you can shape it to your surfboard's contour so you don't have to sand it which can be a little tricky since it's harder than the foam and the intersection of the repair and foam will be difficult to get nice and smooth.

Sand off the resin and foam pieces stuck to the fin box and you can re-route and reset the fin box correctly. You'll be routing into a hard resin repair so go slowly.

If you want to hide the repair you can put more sealing paste and paint over it with acrylic paint or do an opaque color resin lamination.