How did C.C get her scar?


In Code Geass, when we see C.C mainly topless we see that she has [a
scar](https://i.stack.imgur.com/Xz1m3.jpg) on her left breast.

The first time we see this is when Lelouch tried to get C.C to move away from
the Lancelot when she's feeding Suzaku shock images to destabilize him. when
Lelouch touches her he sees her memories and there is a scene where C.C is
naked in a river and there is a close shot of her scar.

However in the scenes were we see when C.C obtained the Code I can't really
see the scar on her when she's in the church naked talking to the nun who gave
her Geass. After C.C is covered in blood from killing the Nun who gave her
Geass i still don't see the scar.

The scar itself kinda looks like a trident and not the Geass Sigil which
questions if it's even linked to Geass itself. So i am wondering, when and how
did C.C get this scar? also given how she been shot in the head and stabbed
with shrapnel and healed completely how come the scar hasn't healed as well?




Firstly, C.C. did not kill the Nun. The Nun's intent was to force C.C. to take
her Code, and once C.C.'s Geass matured, attacked her to make her do so, and
then killed herself. C.C. receives her scar from the Nun, during that
altercation.

Presumably, the Nun tried to draw a Geass symbol, but it was done imperfectly.

Presumably, the scar persists because it was one of C.C.'s features before her
death, so it doesn't go away completely.

