It happens to the best of us. First, do you have any extra backing?? Is there fabric left over from the quilt that you could sew a strip on the top and the bottom?? I am disable and this is always happening to me. Batting is real simple. If you have excess on the side, cut it straight with a rotary cutter and match it up on the short edge. I use a 3 or 4 inch fusible lightweight interfacing and iron it on. I have won ribbons with quilts that I had to add batting to and the judges can never tell. Relax and then start working on it when you have worked the "UUggggggghhhhhhh" out of your system !! You have a darling baby as your avatar. I miss my Westie so badly but I am no capable of taking proper care of a dog anymore.