Hello there ,
Thanks for writing your query,
Swelling in the cheeks post root canal treatment
suggests incomplete removal of infected pulp tissue in the root canals that leads to spread of infection to the surrounding structures and in turn it leads to formation of abscess or a lump .
i suspect some remnant of the infected pulp tissue has left unexplored during the root canal procedure or there is a missed canal due to which the infection has gone worse and you have developed a periodontal abscess
due to spread of infection to the underlying tissues.
This type of periodontal abscess drains in the oral cavity and may lead to nausea
once the abscess is drained the infected tooth needs to be explored again for root canal procedure.
you need to get an x ray done the affected area to confirm the presence of infection, approach a dentist
for the treatment.
i hope this helps ,