Cop pulled me over and...?

Okay well I got pulled over recently by no apparent means, I was going 60 on the freeway (which is the speed limit) and there was a cop car besides me along the way, not following me but just stayed besides me for about 5 minutes. I could sense that he was going to pull me over, in which he did. So I asked him 3 times on why he pulled me over because he kept on changing the conversation, and he came up with 2 excuses, my cars headlight was out (total Bs) and I was stepping on the line, psssh don't we all!?.. So he took me out my car, pulled me into his, asked me questions, and then he asked me for insurance like 20 minutes after, so I told him that it was inside my car, so he went to get it and when he came back he did some computer stuff, 10 minutes later he asks me that if I smoked weed, which I dont, I told him no, and he said if anybody I know did, I said no. So he asked me why was there Marijuana stems inside my car, I told him I had no idea, because nobody I know smokes, let alone myself. So he was totally Bullstiin, I got pissed, he then said that he would show me what he was talking about. Well at the end when he let me go, he never showed me the Marijuana stems, and I would like to know if I could sue him for saying $h!t like that, false accusations or something, because well first of all he pulled me over for basically nothing, my car is suspicious because it's a sports car, maybe that's why he did it.. and well he said I found something in my car that was totally not true, not even worth mentioning. I want to sue his *** but I want to know how because it has been bothering me ever since, and I cannot get it out of my head, and I have been having dreams about such incident, I have never tried Marijuana, alcohol, nor cigs. I am clean. Thank you.