Raise and support a sunken laminate floorboard without removing the entire floor?
I had something similar done on two different floors (solid wood herringbone parquet and more recently on an engineered wood floor). I assume the same trick will work for laminate flooring (given that it's pretty similar to my engineered wood example).

The trick was to use low expansion polyurethane foam to fill in the voids underneath the flooring. The foam comes in a can ending with a ~2 mm diameter pipe, so all you need is to drill suitably sized holes into the floor, stick the pipe in and carefully inject foam until everything is level again. Of course you can't do this with ordinary PU foam as that expands a whole lot and would rip your floor out.