There's a probability that the RCT might not be properly carried
out. There could be another probability that some adjacent tooth is also decayed or worn out that's giving you the sensitivity. Try contacting the dentist
who's done the RCT and get yourself evaluated for the symptoms. Just in case the RCT is not properly carried out, it needs to be re-done, Meanwhile try using an anti-sensitivity toothpaste like Sensodyne or Colgate Sensitive.