Adding additional jarrah floorboards

After removing a horrible brick fireplace hearth, my wonderful 72 year old father in law has added additional jarrah floorboards (same width and colour as the original found at a salvage yard) to continue the flooring (parallel) to the wall. However the join between two sections of floor is not good for two reasons: 1. there was a quarter round between the brick hearth and the original floor and of course this means there now a strip (25mm) where there is no floor finish 2. the last original board had no groove and there is a 1 to 2mm drop from last original board and the first additional board .

I can't possibly ask father to rip everything up and remove last original board and then relay all the additional boards. I haven't got the skills myself!

Thought of sanding the last board and all the additional boards and re-finishing.

Any ideas?
Thanks
Ian

If you cant do it yourself and dont want to get your dad back in, the you need to ring a floor sander who can do board repairs , you will locate one in the yellow pages. He will fix the problem and finish it of for you.