Normally after a root canal treatment the tooth remains tender for a few days.Before getting to any conclusion we would like to see some x rays of the tooth in which root canal has been done.Visit your dentist again and tell him/her about the pain.An iopa xray might be necessary for the evaluation of pain.
Next Steps
visit the dentist again and tell about the pain,x rays are mandatory. you can post it here also so we can diagnose the reason of pain