If it were at the stern, I suggest just leaving it as-is. However (even though other folks will hardly notice) you will be looking at that strip when you paddle. It would 'bug' me; you may be more laid-back! :-)

If It were my project, I'd probably tack (with hot glue) a nice wide guide strip (a 2-3" wide strip of 1/8 plywood?) to the deck and use a router to cut a new groove for that midline stripe. The smaller the router, the easier for that kind of job. You can size the strip to fit the groove - if you don't have a thickness sander/planer you can improvise something- check out luthier sites for jigs to thickness binding and purfling strips.

If your shop humidity is reasonably stable, I'd suggest glassing the inside of the deck if you have popped the deck free of the molds already. It may be in a quite fragile state right now, or not?

I'd use epoxy to glue in the new stripe, but that will/might cause problems with your staining plan, so probably yellow glue would be better. Leave the stripe proud of the surface and plane/sand it flush later.

If the new white stripe still doesn't look OK, I'd replace it with a cedar one - you'll still have a subtle 'centerline' but mistakes won't be so obvious.