A personal headcanon of mine (and the only other piercing I can think of Bon having at this point in time):
Originally I just thought that he would only have one nipple pierced - but considering his ear piercings are so symmetrical..maybe he gets them both pierced? (I like him best with just one though <3 )
Later in Life:
I hope he gets a Daith piercing to help with his migraines (that I’m almost 100% certain he has!)
I’m also pretty convinced that later in life (when he’s like…I dunno, 18 or something) he’ll get his right eyebrow pierced.
I think he got his piercings for many reasons but none are very deep:
Rebelling (against his parents and society and what not)
to look cool (its the first thing Rin said about him afterall)
to stand out/uphold his image
he probably genuinely enjoys body art such as piercings and tattoos and thought for a long time about what he did want on his body
(No, I do not think Bon got any of his piercings by losing a bet with Shima.)
I’m also fairly certain he changes his piercings to things he believes would heal him. Like changing the lobe piercings from just the metal to studs (or dangle-y) earrings with specific crystals/stones on them that has specific healing powers.
Because According to this:
Lapis Lazuli helps battle migraines!
(He would never be caught by anyone other than Konekomaru or Shima wearing dangle-y earrings though!!)
I’m certain he has all different types of healing crystal/stone earrings. He knows how each one helps him and keeps them in a earring box hidden in his drawer.