Head hurts

Ok guys yesterday my nephew pushed my 6year old to the ground slamming his head hard on the concrete my son not has a big bump a fever an neck pain. I’ve never dealt with this. So would I need to take him to the ER just to make sure his okay. I did tell my sister what her son did but my sister is one of those bitter ass parents who “My KiD iS aN aNgEl He NeVeR dOeS nOtHiNg”.