Toothache starts over a month later after a deep filling

In February I had a deep filling done. It’s a temporary filling because I am in need of a root canal. Anyway, after about a week I didn’t experience any tooth pain. However, 2 days ago on April 18th my tooth became sensitive to cold and hot things and I can’t go to the dentist due to the virus outbreak.
Has this happened to anyone?
What could I do to relieve the pain and sensitivity?