Can a tooth be infected under a crown?

Tooth had RCT done and food trapped while temp crown on. She cleaned and put permanent crown was put. After a few days i have pain around ear, neck, jaw etc. went back adjusted the bite. It smelled bad when i floss. Now after 2 days pain still not getting better... my gum is swollen. She said wait for at least a week... black area was shown in the xray around crown and gum line. She said keep it clean floss well.. i am not sure if she needs to redo the crown? It is infected? Any thoughts?