I did this to a quilt top one time. Try inserting a piece of, OMG I can't think of the name of it, the stuff you use for applique. Slide it inside the cover,big enough to cover the entire cut. Then press with a very hot iron. Make sure you get the edges of cut meet identical. The top I did this to was a wall hanging. You cannot tell was it repaired. Let me know. I have one of the cut and sew. I love mine. Can't do without it. Pam