Thanks for asking the query,
After a sucessful root canal treatment
the canals are removed and the tooth is completely devitalised so there are no chances of pain.
There are chances of pain radiating from the infected tooth to the cheek, ear and neck ,i would suggest you to get an x-ray done of the affected tooth.
Also look wisdom tooth on the same side if crooked, impacted or crowded can lead to pan in the cheeks.
Another cause is allergic reactions, inflammation of the lymph nodes, any blunt trauma
to the face, inflammation of parotid gland
, growth such as tumors cyst can also cause such type of symptoms.
I would suggest you to get a complete clinical evaluation by the Dentist
to confirm the cause and plan appropraiate treatment, if the tooth is reinfected you habe to go for re-RCT of the tooth.
You continue with the course of antibiotics ans analgesics and maintain a good oral hygiene
Hope this helps out.