My 5yr Old Son Pushed My Husbands Neck To The

My 5yr old son pushed my husbands neck to the side forcefully while my husband was sitting on the floor and then jumped on his head...my husband's neck now hurts and he has a lump about 2/3 way down back of his head about size of 1/2 golfball...he says he feels like he pulled something and is very uncomfortable. Should he be concerned?