Find the strand that you pulled through and pick it out of the last loop that was left on your needle.
Find the stitch that you passed over to bind off and lift it back over the last stitch. Keep finding the passed over stitch and lift it over the stitch that it's around. If you take a close look at the bind off you'll see that it's basically one loop inside another inside another. You just have to take the outer stitch off the one that's inside it.
If you slip a needle or piece of yarn through the stitches as you get them undone, it'll save you the worry of unravelling.