I recently started a scarf for my sister, and was not used to the type of yard I'm using. Subsequently the initial quarter of the scarf is rather loose, and it's apparent as I continued knitting, that I became more comfortable and the stitches are more even. My question is: is there a way to go back and tighten those earlier stitches without undoing the entire rest of the scarf? I'm not worried about perfection, but do want it to look even. Thanks!