Suggest Remedy To Relieve Headache And Vomiting After Being Knocked Unconscious

My son was attacked and knocked unconscious on friday night he was taken to the hospital as he started to vomit and couldn't remember a thing, they checked him over and after about 4 hours said we could go home. He didn't tell us what to look out for and I am worried as he has slept constantly, was being sick until Sunday morning and can't really eat anything ( has tried 2 bites of a bit of toast a couple of times but felt really sick after) He didn't have a headache at the hospital that started Saturday afternoon and has got worse, now paracetamol is not helping and he is feeling worse. He doesn't want to go to the hospital as he doesn't want to be left on a chair for 4 hours again when he's feeling so ill.