Assuming its a good brand of memory card, the manufacturer will replace it.
You can do a erase of the card and reformat it, which should mark any bad cells, A full format in a computer might do the same.
Formatting in camera does not actually do anything, except change the FAT table to tell the controller that the card is empty and does not fix any issues. It is a good idea to format in camera after doing a full erase, because the camera creates the necessary folders.