I could be wrong, but it looks like you have way too much fabric at the corner. This could happen if you don't fold the corner over just right when sewing to the front. When that happens there's nothing you can do to make it right, other than un-sew the binding from that section of the front and re-do it. It would probably mean putting in another piece, since you would need to cut the binding on one side and re-join so you don't have extra fabric.