I'd use Loctite 420 or Hot Stuff CA glue to bond & seal that spot. Hot Stuff comes in 2 or 3 different viscosities-- you want the thinnest (wateriest) one. Just put a drop on the edge where the separation is, wait just a few seconds, and wipe off the excess from the surface of the bow. The glue should wick its way into the spot. You may need to repeat this (probably only once, if at all) to completely fill/seal the separation.
The reason I say to wait just a few seconds before wiping the excess glue away is that you don't want it drying/staying on the exterior surface of the bow. It's kind of a balance-- you want to give the glue time to wick into the separation, but you don't want remnants on the exterior surface. You should be able to let it sit for up to 10 seconds or so before wiping away. If you just use a small drop, hopefully most all of it will wick into the separation anyway.