welcome to HCM forum,
i will be glad to answer your query,
first of all i would like you to know that whether a tooth requires RCT or not depends on the extent of infection in the tooth , which can only be confirmed with tooth x-ray. I am not too sure if your dentist
did an x-ray of your tooth. I do not know what was the condition of your tooth a few months ago, therefore i will not be able to provide you with the reason as to why your dentist did not perform RCT before.
It is advisable to perform a root canal treatment
if there is a doubt of infection in the deeper layers of the tooth.
I will advise you to get root canal treatment done for your tooth by a specialist(endodontist).
If pain and infection are present then a complete course of antibiotics and anti-inflammatory medication will be prescribed by your dentist.
Do not worry, kindly visit an endodontist soon to avoid infection from spreading further.
i hope this answer was useful,
i wish you good health.