If you did a regular bind off where you knit two and then lift the first stitch over the second one it is easy. Did you already cut the yarn and finish off the last stitch? If you did you need to get the end stitch undone and from there you can just pull on the yarn and each stitch will undo one at a time.
Depending on how brave you are about dealing with stitches that are off the needle there are several things you can do. You can undo the whole row and then reinsert the needle into the line of live stitches. Or you can pull slowly letting one stitch at a time pop out and put it back on a needle. Or you can even tink the stitches one at a time back to a needle.
To tink back: When you have undone the end stitch (if you do method A below) you have a free loop sticking up on the top at the end of the bound off row. Around its base is kind of a noose that forms the end chain at the edge of the bind off. Under the loop and the noose is a hole that is the last stitch you knitted into. * Stick a free needle into the hole that is the center of that stitch below the noose, from front to back, then pull gently on the tail and the first stitch will pop loose and you will have one stitch loop on your needle and a new end loop next in line ready to be undone. Repeat the part after the * until you have tinked all the stitches onto a needle. If you have trouble seeing where the stitch hole is that you are to put the needle in you can put the free loop at the end of the row on a needle and pull up on it a little and it will open up the hole better so you can find it more easily. If you work that way, as the new loop pops free you can immediately stick your empty needle into it so that you are ready to do the next stitch.
By the way there are two ways (maybe more) to deal with the final stitch of a bind off. (A)The way I've always done it is to cut the yarn, take the needle out of the end loop, then pull the tail through it and snug it up. (B) Is to cut the yarn and then to leave the needle in the loop and pull up the loop until the tail pops loose.
I was just experimenting with both of those methods and you have to undo them a little differently. (A) You undo by opening up the loop and pulling the tail back out of it so that you have one loop at the end again. (B) You have to pull the tail back through the end chain of the BO and then it will be running through the last stitch you knit to do the BO. You have to take the tail out of that stitch and then you can deal with the rest of the row.