You may have accidentally created a yarnover where you didn't intend one, or you may have dropped a stitch. If you pull along the sides of the hole, a dropped stitch will continue to drop; a yarn-over won't. You can easily fix a dropped stitch with a crochet hook. Go here
and scroll to 'fixing mistakes'.
The accidental yarn-over, though, will leave the hole unless you frog (rip out) to the problem area.
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