A pain in the back of the last tooth is usually a symptom of pericoronitis. This means that during the eruption of the wisdom tooth, it causes a blind pocket to form between the surface gum flesh and the wisdom tooth, and food embedding and bacterial growth occur, triggering a bacterial infection between the wisdom tooth and the gum flesh. The infection can spread and cause swelling of the face and possibly fever. Intravenous fluids or oral antibiotics, such as cephalosporins or macrolides, along with metronidazole or tinidazole, are usually required. Intraoral gargles, such as 0.12%-0.2% chlorhexidine gargle or rehabilitative gargle, are usually used. You can also use sprays or topical rinses, such as 2% hydrogen peroxide or 0.9% saline for rinsing, and topical application of iodoglycerin or minocycline on the surface to promote its absorption and healing.