The cast on edge of a blanket was pulled together after
washing. When I was stretching it the yarn broke. I have the stitches on the needle but now I’m
wondering how best to bind off the cast on edge?
Have you taken out the entire cast on and can you then bind off the cast on edge the same way you did the bind off edge? That way the two would match. This is often done deliberately by doing a provisional cast on, later removing it and then binding off so that the two edges match.
Simply attach new matching yarn and BO. The stitches will be 1/2 step off, because you are working in the opposite direction, but no one will notice as it is a CO edge. Weave in ends.