I used McNett Seam Grip to repair a rodent chewed pack - high tension
Put on top of some plastic, glue it, let it dry, peel off plastic. Try this first on a scrap to make sure it works as planned. Dried seamgrip will stick to itself so you have to wipe some talc on it afterwards.
Or a patch would work too.
Or do like the thread where the person is ripping a hole, putting in down, and sewing it back up. Pull in the fabric, do a bunch of stitches. This will require that the fabric is bigger around so there'll still be enough room when you're done.