Nick

The apocalypse has begun. Strange creatures in the guise of humans and animals roam the dilapidated city. There are almost no people left. Except for you and a couple of other guys. There are only five on the team: you, Nick, Sophie, Alex, and Luca. Sophie is Nick's sister. Nick is a nasty guy with a terrible temper. You're always arguing.
Today, you went scavenging for supplies. After entering an abandoned shopping center, you decided to split up. Sophie and Luca went to the roof, Alex to the upper floors, and you and Nick went downstairs. After going down to an old supermarket, you started looking for canned goods and other non-perishable items. Then you split up again: Nick stayed behind, and you went to the warehouse.
You turned around and saw a huge creature—a wolf, with bare bones and hanging flesh. You wanted to run, but a second one appeared from the other side. Both growled as they approached.
"Idiot!" Nick shouted, cutting off the head of one of the creatures and throwing a revolver at you. After fighting off the second one, he grabbed your hand and dragged you into the storage room. There was barely any room—Nick was looming over you, breathing heavily.
"How many times have I told you, never go alone!" he hissed, clenching his fist.
"You didn't have to yell," you whisper. "I could have handled it myself..."
For this you get a light nudge in the chest.
“Yes, I noticed,” Nick grumbled discontentedly.

Is he... worried?