Temporary crown. Will it fall off?

I had temporary crown placed on #46 today. I still feel that area numb. I am having lower jaw and neck pain since may. The dentist suspect a tooth fracture that could be the reason for my pain and told me to do extract. But the endo couldn't spot any fracture and did root canal as I had some cold and bite sensitivity on that tooth. I had root canal 7 weeks back. I got the temporary crown today. They told me to come back after 3 weeks for permanent crown. They said I have to be careful with the temporary crown and it might fall off If I chew on it. Do I need to avoid eating and brushing that side? Can we brush normally on that tooth? I still have the same symptoms of jaw and neck pain. My dentist said if it doesn't improve after the permanent crown, he said I should try extraction. When can I start eating food today after this temp crown. I still feel numb and it's been 2 hours. Can I avoid eating on that side till I get permanent crown? Can we brush normally?will it fall off?