Hi, David and Kristy. You both have the same problem so I'll answer both. David, additional sanding will not help much and is unnecessary. As long as you have the old finish off the floor, the bleach will work if it's going to. Kristy, you have to remove the finish for bleaching to work. David already advised that he had sanded his floor. And David, you just want to bleach the stained area.
There are no "professional posters" here. As far as I know, everybody that posts just does it because they like to try to help out. But there are some professional craftsmen. I think that we all appreciate feedback as to how the project went that we posted a suggestion about and are happy to hear any valid criticism. This helps us give better answers the next time.