Probably the best thing to do is to repair the hole by figuring out what caused it. It could be an accidental yarn over which would have added a stitch. You can knit over to the column with the error and ladder down to it. If it is a yarn over, you can just continue knitting the current row. The extra yarn from the ladder can be worked into the side sts and won't show.
If you can't figure out what caused the hole, you can always take some yarn or some sewing thread and close the hole up from the wrong side. That can work amazingly well, even with stockinette.
There are some very helpful videos on the Free Videos tab under Tips, Fixing Mistakes. You might take a look and see if they help.