How to deal with reminats of father in-law's help.

Father in-law wanted to help, so on a weekend we were out, we said he could get the plywood and sort the floor.

He managed to find some cheaper board that's 4x as thick as the board we were going to put down, so he bought and installed that.

We now have this gap with the board higher than the carpet. We have lino to go ontop of this, and enough of-cuts to full the gap, but unsure if there are metal trims for this or if I should try and slope down to it or something?

Thoughts appreciated, thanks.