I have a possible solution for you, depending on your skill and confidence level. First, pick out the quilting a little on either side of the tuck, maybe 1/8-1/4 inch. Then gently push the fabric from one side under the other side so that the tuck is inside and the seam appears straight. Next, slip stitch the new seam together. Lastly, re-quilt the quilting over the new seam. You will need to be careful with your start and stop quilt stitching so it doesn't look overstitched. Does that make sense? If not, let me know and I'll try to explain it better.