For those whose kid had a bad concussion, what worked for us was time. Get off the pitch. Avoid anything remotely close to a headache trigger. No bright lights, no music, no tv, no hard thinking. Play little kid games, talk with them, read them a book. And let them sleep whenever they want.
Migrelief helped a bit with the headaches. I recommend trying it, but it’s not a cure. It just helps your head not hurt while you wait for your body to heal.