I agree with Paper Princess, remove the quilting from at least a square foot, maybe even 18 inches, pin vigorously distributing the fullness across the entire area you have frogged, then quilt slowly over the area - starting in the center of the area (maybe follow your previous needle holes with a blue fabric marker so you don't lose the pattern) and leave the pins in until you absolutely MUST remove them. I quilt on a longarm, so I am basically telling you what I would do in a similar situation. You will end up with a little fullness spread out all over the area you picked out so it shouldn't be as noticeable.