You may have to do 2 rows to find the error, but be that as it may, it won't be too bad. Since it is only 48 stitches "Tink" it (Knit backwards
). That means undo each stitch 1 by 1. This is better than ripping the whole row out, because
1) it is seed stitch and you will have to move the yarn front to back as you go.
2) you may find the error only 10 stitches back rather than all the way back.
3) you won't have to worry about twisting stitches when you pick up the loops of an entirely ripped out row.