Only person you talk to in a cl ignores me?

I sit next to a friend in cl, he's being a little kid and ignoring me for stupid reasons. I don't know a lot of people in this particular cl, so I he was the only one I talked to. Now he hates me, he ignores me (I sit RIGHT next to him) and talks a LOT more than usual to all the people around us (people he knows). It's really awkward, I don't say a word in cl anymore because of this. He constantly cracks jokes, flirts with girls around me, and touches guys a lot in a brotherly way. Basically, I look really isolated. If I try to talk to people he'll diss me really bad. What do I do? Being socially isolated in a cl makes me not want to go.