My son hit his head he has a big knot its blue I put ice on it but it hasn't gone down will he be okay should I take him to er?

Bump on head. If your son did not loose consciousness and is actind normal including no headache, dizzyness, unsteady gait and has no nausea or vomiting then all you have to do is put ice one the bump, which a hematoma, which means bleeding under the scalp and that is not serious and gradually the hematoma will get smaller and disappear as blood is absorped back in to your body.So continue what you are doing.