Nikki is naturally very hot to the touch, and flammable things that have come into contact with him while he was angry have been known to burst into flames. His touch also burns flesh if he’s worked up enough. He can only regulate this when in a steadier emotional state.
Nikki has an intense and embarrassing asphyxiation kink. If he panics and tries to rip at your hands, don’t worry, he still likes it— the adrenaline that comes with teasing death.