Thanks for posting your query.
The root canal
treated tooth may be re-infected causing sinus infection
I would advice you to get clinical as well as radiological examination done.
If the infection is severe,tooth has to be extracted.
If the tooth can be saved,re-rct can be done.
Apply hot packs.
Avoid intake of too hot/cold fluids.
Maintain oral hygiene
Please do visit your dentist
and get further treatment done.
Take complete course of antibiotics after consulting with your dentist.
Hope this helps.