Is the binding that you've already sewn up a straight strip, or is it too shaped into scallops?
If the binding is a straight strip and the scallops on your quilt are narrow and/or deep, you might want to recut the binding as bias.
If the binding is a straight strip and the scallops on your quilt are wide and shallow, say 6" wide and less than 1" deep, you should be able to get away with the straight strip. You'll have to ease it a little to get it to lay flat but should still look good when finished.