Nobu was one of the most dangerous adversaries Daredevil faced in Season 1, an expert in martial arts who came very close to defeating Matt Murdock. He was left burning to death, but we didn't actually see him die, and now it appears as though he is back. Granted we don't definitely see him, but it looks a lot like his weapon that appears as Stick is talking about his hand, and that man taking off a mask seems very likely to be him. Given that he's apparently working with the Hand here, there's actually a strong chance that he did die, and has been resurrected by the organisation, which is an exciting development for the show to bring in, and means we should be set for another great showdown between him and Matt.