lol dont worry about it. my bunny did that too about that age. it is puberty lol. my suggestion is to get him fixed.
1) will be calmer and not so aggressive
2) wont start with spraying to mark his territory (it's a pain in the butt to clean every day from the walls around his cage)
3) healthier for him
4) wont be so hormonal and want to hump everything (unless to display dominance of course)
and i'm sure there are a few other reasons to do it, but i'm kinda tired right now and cant think lol. now none of these are guaranteed to happen after bunny gets fixed, though getting him fixed should help at the least.