What Causes Pain In Head And Inflamed Tonsils In Children?

Grandson, will be 5 this June 7th has commented his brain hurts, this past Friday evening and again at 3:00 AM Sat. morning. Our daughter took him to the ER around 3:00 PM, had a brain CT scan, ok, tested for flu and strep, negative on both however stated he had inflamed tonsils. Basically did all tests except a spinal tap.Felt better today, had some fever but Motrin appears to help bring it down. Daughter just called and said his fever is back! Go back to ER?