A short distance away from the nails saw across the damaged board. Place a strip of wood under the raised section of board to support it. Lever the board at the other end and remove all of it, or saw the other end of the section to be replaced in a similar way. Attach softwood battens across the joists to support the ends of the replacement section.
Check the width and depth of the new section is the same as the rest of the floorboards. If the new section is not as deep as the other boards it can still be used by packing the end battens with plywood or hardboard before positioning the new section.
If you need to cut across a board that lies close to a wall, take care not to damage the bottom of the skirting board. If you do not want to remove the skirting board, drill a starting hole through the board along the side of the joist. Use a power jigsaw or the blade of a pad saw to cut across the board. Attach a softwood batten across the joist to support the replacement board and continue as above.
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