Abatron.

sanding and scraping should work. an on site trim carpenter can straighten it out....should be looked at in person. youd want to use the pieces you have because of the cut the floor now has around the section. the only awkward thing is if you take it down / apply the rectangular piece and you have a gap at the floor the quarter round does not sit as perfectly.......it can be dealt with . main thing is get that rectangle section cleaned up and finished. new rounds at the floor/ were you doing that anyway? Get someone.

I need to find someone for sure! thank you