What could this pain under veneer in tooth with root canal be?

Had 2 front upper veneers replaced a year ago. 4 months later needed root canal in one of them due to pain and sensitivity. They felt fine until December when I got Covid and developed tooth ache under the veneer in tooth with root canal. X-ray confirmed RC was fine. I had 3 bite adjustments and feel better but the pain is not completely gone. No pain at night, I wear night guard, no pain during the day if I wear night guard. Pain goes away after hot shower. What might it be?