It is most likely at either the left or right side of the sock. See what the pattern tells you - remember when you were knitting the sock, was your start of round at the left between the sole and the (patterned?) instep or what?
If you can't remember, see what the pattern says. If the directions said Round x, knit half the stitches flat, knit the second half of the round in pattern stitch, then the start of the round is on the left side of the foot.
But it doesn't matter too much where you start, it will not make the sock lopsided if you pick a new start of round at random.