The only way to dissolve the dried polyurethane is with strong solvents. This would also remove the finish from your pre-finished floor.
One possibility is to use fingernail polish remover, acetone, to soften the polyurethane and gently scrape it up with a plastic putty knife, to reduce the scratches. If a scratch kit is available from the flooring manufacture you could use it to reapply a finish to this area. You could also try a wood finish restorer like <a href="//www.painters-toys.com/clear-wood-finishes/wood-finish-restorers.html" target="_blank">Howard's Restor-A-Finish</a> of the same or similar color.
Try this first in an area that is normally hidden with furniture.