2 things u can do. Go back to your workshop and do as follows:
1) They will reset the ECU and the light will disappear. You can try driving for a while and see if light reappear again.
2) If appear again, your o2 sensor is faulty. IT cost 200 - 300 depending on the effort to change the 02 sensor.
Mine 02 sensor was faulty during CNY. Damage around 320 to change.
So what should I do about it??