My Son Had A Mild Concussion Yesterday. He Was Hit

My son had a mild concussion yesterday. He was hit hard on the top of his head with the fist of a special needs student that he was teaching. He saw stars and was driven to the hospital. He was diagnosed with a mild concussion - no LOC. Today he is tired and running a fever of over 101. Could the fever be related to the concussion or just a coincidence?