Suggest Treatment For Symptoms Of Concussion

Hello, I m Hailey. My ten year old little brother had a concussion about three weeks ago, he went in to the emergency room because of it. Anyways my brother was brought back to the hospital and they cleared him for healed, but today he started experiencing a really bad headache at about noon and started feeling nauseous at around seven pm. Our family also has some kind of bug going around, my one year old sister and seven year old sister both have a pretty bad cough with the younger having also a snotty nose. My mom and dad both have a really bad sore throat. I m the only one not sick. Is the way my brother feeling a result of his concussion? Was he actually not healed and he did too many active things causing his brain to hurt. Or is it just symptoms of the bug? Please help, I m really worried about my brother...