I have root canal retreatment 3 days ago. Constant pain in that tooth but nothing found on the cbct and xrays. Had first RCT in2020 but no infection on tooth that time. Tapping and biting pain on it. Had partial distal root retreat in 2021 and no relief.  Endo reopened one last try to see if anything wrong 3 days ago. And told me to extract if nothing found. He reopened and saw one root in mesial was having wetness in canal fillings and stinks.he said blood color was like purplish and not blood red. He put medicine inside and asked me to take antibiotics for ten days. Told me to come back after 6 weeks for second step. Is this blood color changes means serious infection? Will this cause sepsis? I am worried about it. Taking penicillin VK 4 times a day. It's been 3 days completed now and still have pain in that tooth. Always sore pain and sometimes sharp pain. Is this normal? Do we need to pull that tooth if root canal is infected /failed?