4 days ago I did rct on infected& coronal leakage teeth 11.Filled temp cotton pellet & cavit. Perm filling & bu appt in 8 days. Any risk of infection?

Depends. If the tooth was effectively treated, and all the infection gone, then you should be fine. By waiting the time you have indicated, you should have a good idea if things are ok. Much depends upon the state of the tooth/infection when the rct was done. Sometimes, the endodontists do not fill/seal @ the same appt. Then they have a chance to re-eval before filling/sealing (completing the rct). Ask.
Possible. From the information that you supplied it is possible for an infection although the risk is low. I'm assuming the canal was properly instrumented and that you were placed on antibiotics to control or prevent the spread of infection. Your own dentist who actually treated you is most aware of the specific situation and would also be the one to best answer your questions.
Low risk. Of the endodontic therapy was sealed properly and the temporary intact, the tooth should begin to heal. At times antibiotic therapy is required only if the infection has spread into adjacent tissue.