I would slip a piece of fusible underneath the tear and fuse it closed. You can also applique a small decorative piece on top of it (can do this even without fusing first). You can even applique a patch of the border fabric so it blends in. I'd just be sure to quilt over the patch.
Edit: If you have a two-sided fusible on hand, you could take a piece of scrap border fabric and fuse it underneath the tear. This would hold the edges together and would be very unnoticeable.