If the pain is significantly increased on the 4th day after wisdom tooth extraction, you should pay attention to observe whether there is redness, swelling and overflow of pus in the extraction wound, because there may be post-extraction infection. Wisdom tooth extraction involves gum flap, bone removal and root division, suturing and other operations, which are relatively more traumatic and longer, and there will be significant pain after the operation, but the pain will gradually decrease with time. If there is a sudden pain on the 4th day after extraction, it is possible that the extraction wound is infected due to poor hygiene or the lack of good application of antibiotics during the perioperative period of wisdom teeth, which may lead to redness, swelling and overflow of pus in the extraction wound and corresponding odor in the mouth.