How can i tell if i have a bad head injury? i hit my head kinda hard on my the front left side. it's sore.

Other symptoms : One of the most important things to know is is you lost consciousness after hitting your head which is a sign of a severe concussion. Other symptoms are headaches, problems with concentration, sleeping problemss etc. If this last more than a day you should seek medical attention and get a ct scan of the brain t ensure there is no structural problem (ie bleeding).