Looks like it's loose enough that you can tighten the existing material. First, separate/untie the knot, which will be at the lower end wedged between the leather and the foam. Then, starting at the top of the quiver, tighten the stitches by hand (By puling them tighter. Don't pull them out and restitch.) and retie the knot when you get to the end.
If the stitching is cut somewhere, can take it out, paying attention to the stitching pattern, and restitch with artificial sinew, which is what is used in the original. Good luck.
Oops. Looked at your picture again. Looks like the problem is on the lower bracket, not the hood. Regardless, process is the same, except the knot will be hidden the leather and the metal arm.