That is an adorable baby quilt. The bright colors are perfect and I know how frustrating it is to get to this stage and run into a problem. Unfortunately, just by looking at a photo it is hard to tell how crooked or stretched the borders are but my recommendation is to removed the outside border, make sure the quilt is square and flat, re-measure for your final border and reattach. Judy's method for measuring is spot on. Your quilt is beautiful and I am looking forward to seeing it completed.