There's no one right way to deal with a problem like this and different approaches give varied results that will satisfy different people — obviously some would only be happy if the whole floor were taken down to bare wood and refinished from scratch, and really that's the only way to guarantee good consistency of colour and general appearance.
From the Comments you want to extend the spot treatment to try to blend in what you've done with the surrounding boards so I think you first need to give the floor a thorough clean, this is the only way to ensure you're getting a proper read on the colour you're aiming for. It's hard to be sure from the one image but the floor probably isn't particularly clean even if swept or vacuumed regularly. At the very least the deep grain has dirt lodged in it (it nearly always does!) and as the finish is matt it's a safe bet the surface is a bit grimy (matt surfaces hold more dirt than gloss surfaces). This light covering of dirt will add a slightly grey tone that will throw off colour judgements.
Then if I were doing this — trying desperately not to have to refinish the whole floor :-) — I'd remove finish from a large section where the stains were originally (a dozen boards as you indicate in your Comment above sounds about right) as well as a few random boards a little distance away. Then I'd carefully refinish just those stripped boards, being as careful as possible not to get any finish on top of adjacent floorboards where original finish remains.
Caveat: there's no guarantee this will work well enough, but I am confident you won't be 100% happy initially! Partly this is because you can't know if you're using the same finish as was applied to the floor originally*, but also once you sand or thoroughly clean old wood it returns it to its original pale colour and it takes time and light exposure for those boards to return to the colouring they were before you started. This process will take weeks at minimum, possibly some months, depending on the light levels in the room. And only after this will you know if you've achieved a satisfactory outcome.
*So its colour may be different, but also how it affects the colouring of the wood may be different.
