When bindign off - the last stitch can be used again or finished. In my patterns you will find the following end-stitch.
End-st 1: When you continue in the same col (e.g. on another square), the last stitch is not finished but used as the first stitch of the next square.
End-st 2: When you are continuing in another color, e.g. another square, knit the end-stitch with the new color and this stitch will be the first stitch in the next square. Do not cut yarn until you have woven it in.
End-st 3: When the square is finished but you are going to knit the end stitch later: Loosen the stitch, cut yarn and pull it through the stitch but do not pull it tight (see sketch). This is called a loose end-stitch.
End-st 4: When the square is finished BO the last stitch and darn the tails. Cut yarn.
Is your edge too loose?
Pull the yarn a little tight at the same time as you knit the second stitch (the stitch after the edge stitch) - every time you begin a row on the loose side.
Is your edge too tight?
Make a yarn-over after the first stitch each row on the side with the color changes on right side and then let the yarn-over slide off the needle when meeting it on the next row.