Hello sir... It is not because of root canal treatment... It's because of anesthesia effect will cause numbness on your oneside of lower lip in which you bite that area which causes ulceration and swelling due to damage to minor salivary gland duct of lower lips...

No it has nothing to do anything with RCT, the swelling may be because of some other reasons.

Hello sir, your lower lip swelling may be not because of RCT... After anaesthesia, your lower lips will be numb, so kindly check during numbness if you bite your lips unknowingly it will create an ulcer.... So check wether there is any ulcer in your lower lip... If not kindly consult your Dentist because after clinical examination only we can confirm the diagnosis...