Back pain accompanied by a fever is a symptom combination that requires prompt medical evaluation, as it could indicate a kidney infection or another serious condition. For temporary relief of both the fever and pain, you can take over-the-counter acetaminophen (Tylenol), strictly following the package instructions. Please avoid ibuprofen or other NSAIDs until a doctor has evaluated you, as they can sometimes affect the kidneys. I strongly advise you to see a healthcare provider or visit an urgent care clinic today for a proper diagnosis and targeted treatment, such as antibiotics if an infection is found.