I have repaired some antique quilts. Usually I fix and applique a matching piece/square over the small hole that is torn. I completed a repair similar to yours twice. In this case, first you need to stabilize the front, batting and back. As the lower blocks in the patch are nearly shredded and fibers are exposed, I would not whip stitch it, as the thread will be stronger that the antique fibers and will cause more damage. Gently pick/cut out any quilting around the torn space. Then I would smooth the layers, place a light MistyFuse on top of the back, between the back and batting, and another on top of the batting, between the batting and front. Fuse with an iron. MistyFuse is an ultra light, paperless fusible. After that your block should lie fairly flat. I would then hand stitch (use only matching silk thread-very light) a very basic design (poke stitch - up and down so as not to stretch fibers) meant to hold the three fused layers together. Do not hoop, just stitch. It will be forever weak in that spot and should be treated with extra care. Good luck
Johanna in WI