Road rage assault: cognizable or non congnizable offence?

I was assaulted by a biker who was in an inebriated condition. He used a brick to hit me on my arms and also threatened to kill me. I managed to save my life by calling police but they did not register any written complaint nor instructed me to get a medical done. Do, I have to file a private complaint with court as Police has not been able to find the culprit inspite of having his bike's registered number?