Yeah, it's the cover dowel. If you look, there should be another one opposite of the missing one. (Just a hole). They are like guides. Silicone them in so they don't pop out.
Saying that, I think you're making a big mistake putting 32s on. You're going to be tearing up a lot of driveline parts, like drive shafts, bezel gears, rear diffs. I just wanted to warn you. Good luck.