When a floor board starts to bulge, it's usually because it is warped. Hardwood floors usually warp because they have been exposed to water, or excessive humidity. The water causes the fibers in the wood to swell and shrink. A board that is severely bulged will most likely need to be replaced. If the bulging is less severe, try a couple of simple alternatives to see if you can correct the problem without replacing the wood.
Set a circular saw to the depth of the wood in your floor.
Cut through the middle of board with a cut that is lengthwise.
Split the wood across the board with a hammer and chisel.
Pry out the board with a hammer and chisel.
Measure and saw a replacement board.
Use a hammer to tap the board into place on the floor.
Attach the board to the floor with nails.
Slight Bulging Option 1
Check the humidity in the room with a hygrometer. A hygrometer will tell you whether the room has too much or too little humidity.
Adjust the humidity in your room with a dehumidifier or humidifier
Allow the wood to dry on its own and see if the bulging goes away. Set a heavy object on top of the planks that are bulged to help in the flattening process.
Slight Bulging Option 2
Lay damp towels over the warped boards for two days.
Drill a series of holes every 3 inches in the boards that have bulges.
Insert wood screws into the holes with a screwdriver.
Fill in the holes with wood filler.