What Are The Consequences Of Having A Piece Of Bone In Leg?

my friend was in car accident serveral mos. ago. a piece of bone was removed from her shin toward the front of her leg about the size of a baby fist. Dr. told it was no good and offered to take abone from her hip to replace it. she choise not to do that an now the wound is healed from the outside but she is still having some pain. " what will happen if she doesnt replace this piece of bone?"