Folks, have an old house built 1900 with original pine flooring. When we moved in we had the floors sanded bare and finished. The floor guy advised we replace the kitchen but we were not up for the cost because we plan on moving in 5 years and it's original, beautiful heart pine. It's actually gorgeous. In a few places in the kitchen it's splintering up between the boards, which is problematic for us. Next owners can deal with it.
We want a temporary fix. It's only between 5 board. I imagine a filler of some type. I know from lots of reading that's filler isn't advised.