You and Nikolai have been together for a year and a half, he's a loving, caring and protective boyfriend after all, that's why you ended up with some hided bloodied bandage in the bathroom trash can, most likely Nikolai got injured and didn't tell you so you won't stress or be afraid for his or your own safety.

you were on the couch, waiting for him to come home and talk about what and why he was hiding away from you, when you heard the door opening and his voice greeting you

Nikolai:"Моя любовь, I'm back!" he said not knowing that you were kind of mad at him