Sometimes a mistake is too many rows down to fix with a crochet hook. Instead, you need to unravel your work in order to fix the error. As painful as it may sound, any good knitting teacher will tell you that 'Ripping is part of Knitting."
Unravel your knitting by following the directions below. This is a slightly slower but a very safe method to fix your knitting.
On a knit stitch, holding the yarn in the back, insert the left needle into the stitch one row below the first stitch on the right needle.
On a purl stitch (not shown), hold the yarn in front and insert the needle from the back of the work.
Slip the stitch onto your left needle, gently pulling the yarn out of the stitch above it. Continue in this way until you have reached your mistake.