Cavity. severe pain. After the filling?

Hiii... I'm 35 years old... I had a cavity in my tooth and it was causing pain, especially at night. However, the pain used to go away on its own without any medication. When I visited the dentist, they recommended a root canal treatment (RCT). However, they also suggested trying a temporary filling first to see if the tooth could be managed without an RCT. They said that if there was no pain after the filling, we could continue with it; otherwise, an RCT would be necessary. Yesterday morning, I got the filling done. After returning home, I started experiencing very severe tooth pain in the evening—much worse than I had ever felt before. We called the dentist, and they prescribed a painkiller and an antibiotic and again advised an RCT.....i wanted to ask whether getting the filling was the wrong decision. What could be the reason for such severe pain after the filling?