I started my oak floor installation (3/4” solid oak) at the threshold of a room and completed it to the wall. I’ve now begun the install into the adjoining room in the opposite direction. I glued in a spline and tapped in the board of the next row to ensure the spline was properly seated. It seated so nice I got excited and just started nailing (16ga cleats from a pneumatic floor nailer) and continuing my rows. I had already installed another 5-6 rows before I had some time to think and realized I never fastened the spline, which I’m pretty sure you’re supposed to do.

I’m kicking myself, but am no professional, just a DIYer who does this when there’s spare time. Uninstalling all of those rows currently doesn’t seem like a great option. While not ideal, I imagine face nailing some brads near the spline would be the best solution at this point to prevent that board from potentially buckling in the future? The good news is it’s rustic flooring, so a few face nails could easily be hidden, plus it’s only a 6’ section at the threshold that didn’t get the fasteners. Any other thoughts? Thanks guys.

If there's enough glue used it's doubtful there will be any movement. But as you mention it's rustic. Do what you feel is best, but it may have no effect.

8d nails into the floor joists would be pretty good. It is recommended to fasten at least every foot along the length of the boards, if you can not find the floor joists.