[odog]

I agree with Sequoyah unless you are totally anal and will be driven nuts by the fact that you know it isnt right, dont worry about it. A small grove wont hurt anything if it is on the bottom and an outside board. You said it was Mahagony so I am guessing you wont be hauling firewood or rocks in the bed so weight on the board shouldnt be a problem. Just seal it up extra well when you finish the wood to lessen chances of moisture causing it to crack. If you have to fill it in for your own piece of mind and a new board is out of the question, use doug fir, it is hearty and joints well, also use titebond III as your glue.