Peter Petrelli adopts powers of those he comes in contact with. Eventually we learn he keeps those powers even when not in proximity to the person he's absorbing from. He encounters Claire pretty early on and gets her ability to heal.
In the episode 5 years gone we see future Hiro and future Peter join up and Peter has this slash across his face. We see this slash in other episodes, like in Season 3 when he is caught looking for a gun after his brother is shot.
So much as I can tell, the slash is only there so the viewer can distinguish present day Peter from Future Peter and I don't recall any point where he took damage that sliced his face and didn't heal.
Anyone know how this scar got there and why it doesn't heal?