Once you’ve advanced the film, that frame is effectively lost. On the Nikon FM2, there isn’t a practical or reliable way to return to the exact previous frame position. Film advance spacing and the original loading position aren’t precise enough, so trying to rewind and line it back up would likely cause overlap or double exposure on an adjacent frame.

If this ever happens again and you notice it before advancing the film, you can still use that frame: use the FM2’s multiple-exposure control while winding the lever so the shutter is recocked without advancing the film. Then make the real exposure on the same frame. But after normal advance to the next frame, you should just continue shooting and accept the lost frame.