Board Thread:Theories and Speculation/@comment-5273810-20150207055437/@comment-1018594-20150207200714

Iar Sensei wrote: I always threorixed, since the chapter "Hole", that due to the Zetsu cells (Which do indeed have Hashi's), he couldn't even feel pain.He also states so himself while fighting Kakashi in the aforementioned chapter.

That was in a more metaphorical sense than physical. Remember, that was a genjutsu when Obito was impaled: he meant he's been through so much shit that he doesn't even care anymore, therefore he "doesn't feel pain anymore".