Board Thread:Naruto Discussions/@comment-27863200-20160302112610/@comment-734582-20160302224439

Tengen Toppa Ita-Sasuke wrote: Does Gyuki really respect A that much? I thought that it used to go on rampages. Am I wrong? Of course it goes on rampages, it wants to be free. But a human taking on a Biju 1v1 and not dying instantly? Only a few people have managed that.

As Biju are gigantic masses of chakra and can partially transform that chakra, i think it's fairly obvious that Gyuki can simply chose not to regenerate that horn. I'm pretty sure he regenerated all his tentacles even after them being ripped off repeatedly.