that is a piece of copper. If something came off, the circuit is open. If it is a small break you may be able to bridge it with a solder blob. If it is bigger, you will have to bridge it with a fine piece of wire, like 28-30 gauge.
Since it was damaged, that may indicate that the PCB is very delicate, so further soldering must be done quickly at the right temp.
Scrap off enough of the solder mask with an Exacto knife to solder to, then tin the ends of the traces. If the solder bridges them you are good to go. If not, tin the wire, lay the wire across it and heat. Use a long piece of wire so you can hold it in position, then cut it when soldered.