Every so often your pliers will slip on wire or jump rings and leave marks. If the marks are made by the pliers sliding along the wire or rings and they haven't dug into the metal they can be polished away with either a tumbler, a cloth impregnated with a polishing compound like rouge, or the buffing side of a nail board.

If the tool has dug into the metal, polishing it will just make the marks more obvious. For small scratches sanding with a nail board or fine sandpaper before polishing will erase most marks. These 2 photos are of a 4mm jump ring with tools marks and then after it has been sanded.

For larger scratches, particularly where pliers have dug into a jump ring, or round nosed pliers have squashed the wire, try burnishing the displaced metal back into its original shape. I use the round metal shank of a cup burr in a wooden handle to smooth any gouges. Once the shape is back to normal the wire or rings can be sanded and polished. These 3 photos show the process of getting rid of some small gouges caused by the pliers.

Sometimes big marks can't be erased and the only option is to recycle the metal into something else. I always make this decision under magnification because if it looks good under magnification it will make a beautiful piece of jewelry. Sterling silver pieces can be melted down with a small torch and be used for other projects, the same sized jump rings will make similar sized balls for decoration. Or save up all of your cast off precious metal and sell it back when you buy your wire.