Is that flooring material vinyl? You need a couplbe of strips of vinyl & a nosing.

There's a couple of ways to do it depending on what you can find and purchase.

Some vinyl flooring can be ordered with nosing treads

You can insert some of the vinyl and add a metal nosing like you see below.

Looks like they ran out of flooring and just left the unfinished edge of the flooring which will soon get beat up for sure. If you have no extra flooring and that door covers the transition between the floor and the top step maybe the best bet is to get wood the same as the steps and you will need 2 transitions one from floor to that piece of stair wood and another at the top of the stairs where that wood meets the riser .

Replace the plywood stair nosing with a hardwood stair nosing. Floor guy should have known this.

BeverlyFLADeziner offers a nice solution, here's the look...

"Looks like they ran out of flooring"

Doubtful. It appears something was in place at one point by noticing nail holes in the sub floor. Some kind of custom made saddle/nosing could be created.

I would seek out a reputable flooring/carpenter to explore ideas with you to consider so you don't end up with a bandaid job. The flooring seems kind of skimpy in thickness so not sure how durable it is anyway.

Thanks. It’s actually standard 2.25” red oak stained a lighter color. I guess there is some sort of sub floor building it up that space higher which gives the illusion that it’s thin wood or laminate. But it’s not - it’s normal one!

I'd pry off the metal piece that's held in place with the red-arrow nails. Then I'd remove the black-painted pieces of wood (you can see the seam at the right) which are held in place by the blue-arrow nails. Once those pieces are removed, you'll know what's underneath and can decide what to replace them with.