carefully turn under a small seam allowance (to fold the raw edge inside) you can put a small piece of fusable inside to help hold it- then using small stitches carefully stitch it closed. if you don't mind it showing on the back you could use a tiny zigzag on the machine to stitch it closed- if you don't want it to show on the back then hand stitching is necessary. basting glue or tiny pins could also be used to hold it while you stitch.