Definitely try washing the quilt again in plain water and spin it out. Put in some color catchers to be sure no fabrics are bleeding. Then find a carpeted floor you can stick pins into. Lay down a sheet or 2 to protect your carpet just in case. Start in each corner and see if you can stretch "block" the quilt back into a square. Then pin every couple of inches. Puts some fans to blowing on it until completely dry. THEN I'd resort to taking the border off if blocking didn't work. Hey! I just figured out a good reason not to get hardwood floors.