Cut and remove the damaged portion of the power cable with wire strippers or end cutters.

Take a new XT60 male connector with pre-attached wires (at least 14 AWG) and solder it to what is left of the connected power line.

You can purchase the XT60 male connectors through Amazon or most hobbyist drone shops.

Make sure that once the wire has been reassembled to electrically isolate any exposed wire using electrical tape or heat shrink.