If you're mature enough, you won't be disturbed by such childish
actions. If what you say is true, he's a 15 year old with a mindset
of 12. Just completely ignore him.
Don't respond to his jokes, talks or what. If he pesters you, just
tell him straight in the face to fuck off. If what you say is true,
he can't do shit to you cos you can wack his ass anytime.
If you're not that mature enough to let it go, then shame him
publicly, exploit the holes in his jokes, calling it lame out loud
or what, branding him a dumbfuck or fuck face or whatsoever. Of
course, you're dragging yourself to a lower standard by doing stuff
like this, but from what I see, you're not mature enough.
Only a childish person will respond to such lame shit and get
angered by it.