When to get crown after root canal?

I have severe lower jaw pain under ear, side of the neck and lower jaw since may. I have mild swelling in the lower jaw and side of the neck. I have some small lump spots in the side of the neck and under earlobe which hurts to touch. I have ear pain and fullness. went to ENT and no ear infection. went to dentist, he told me to extract upper wisdom tooth. extracted in July. still the same symptoms. went back and he said I might have a tooth crack in the lower first molar or it could be tmjd.both crack and tmjd will have the same symptoms ,so he said we have to rule out one by one. I didn't feel any pain on lower molar. but during diagnosis, that tooth was very sensitive to cold and to bite on one spot on that tooth. i did RCT yesterday. I still have same pain under earlobe and the side of the neck. so RCT doesn't help with jaw pain. rct helps with sore pain on the lower molar but not the jaw or neck pain. I have severe burning pain. when to get crown after RCT?  told me to get it 6wks.