Crappy photo - probably the torque sensor wires. There's a connector behind a removeable cap on the battery, then take off the chainwheel to get at the back side, then you should be able to solder the wires back together. If the actual sensor got smashed, you can get a new one as a spare part. from halfords, though they're terrible at that sort of thing. There was another supplier (Powerbikes), but they seem to have disappeared recently.