In my opinion if you have pain in RCT treated tooth then it is infected.use some antibiotics and analgesic simultaneously for 3 days BD if problem persist then it will be mostly by Gutta percha point filling RCT, so if you want to quick relief then go for extraction because it can not be saved if problem persist after medicine taken.

Go for xray to determine the cause of pain. Don’t worry,dental clinic are following strict covid guidelines ,no need to suffer from pain. Take ketorol dt three times daily

First we need an X-ray to check due to the time gap between 2012 to 2019 if there has been any leakage or bacterial ingress into the canal as u had not got the crown fitted immediately... it has been a symptomatic for long.... the ideal procedure is to get the root canal done again and get a crown fixed post root canal. Thank u.

Root canal treated tooth may get infected for multiple reasons. Start warm salt water rinse thrice daily. Make sure there is no food accumulation between the Root canal treated and adjacent tooth.

I understand your concern and Would like to guide you. ....... Root canal treated teeth sometimes gets reinfection due to. ..... 1.delayed crown or restoration after rct , 2.sometimes given restoration or crown got crack causing new bacterial infection .so the reinfection chance increases, 3.saliva contamination through the weak restoration, 4.new cavities get formed in the treated tooth if proper precautions are not taken, 5. biting down on something hard to chew food with the treated tooth causing crack formation in the crown of the tooth. .....etc. cause reinfection. In the meanwhile you can take painkiller like paracetamol as a temporarily solution.