easy short cut would be to try a colour wax stick and heat wax a little, use a filler knife to apply can get wax sticks at b&q. or the proper way is to set a skill saw to 5mm start to run saw cuts along the bored 5 saw cuts should do fine but stop the saw cuts 5mm around like a frame, leaver out centre of board untill left with 5 mm frame use sharp chissle between where frame meets good boards, at a shallow angle with a confident tap with mallet aim into centre off frame as this should take out most off frame after this has been done to every side, clean last bits with chissle by hand .now your left with hole for new board, get your new board if same flooring should be one length in your pack should almost fit, make cut down centre of new board to underside full length of the board, two thirds of the thickness of the board then bend as much as possible with hands width ways insert toungue on end of excisting board then remove opposit tongue on excisting flooring with stanely knife, apply even pressure and it should pop in, light taps maybe neeeded.may need a carpenter for this.
mr bond, February 2012