How to Fix Dropped Stitches
An dropped stitch is when a stitch is slid off the needle and not worked when you were meaning to work it, resulting in a irregular section of fabric.
A dropped stitch need not be devastating—it's an easy problem to fix if you catch it within a few rows of the drop. If you don't see it until several inches have been worked, there will not be enough yarn around the dropped stitches to fix the problem, and the best solution is to unravel the knitting back to the dropped stitch and reknit these rows.
Insert the hook into the free stitch from the front. With the hook pointing up, catch the first strand of the ladder from above it (see illustration) and pull it through the stitch on the hook.
Continue in this manner until you've worked up through the rows and then replace the stitch on the left-hand needle, being careful not to twist it. If you've found more than one dropped stitch, secure the others with a locking stitch marker or safety pin until you are ready to pick them up.
Start this video at the 21:11 mark to learn how to fix dropped stitches.
Below: LW3604 His Skull Hat Free Knitting Pattern