Knowing Sirius as he did, even though this wasn't the Sirius that James had grown up with, it would have surprised James immensely if this were only about someone nearly running Sirius down in the hallway. There was quite obviously a lot going through Sirius's mind, and although James had a fair idea of the emotions he was experiencing, he couldn't really guess the cause. There was a lot in this Sirius's past and even in his life here in the compound that James didn't know about.
"My parents really should've just made my first name Dammit and been done with it," he said. "Dammit James, Dammit Prongs, Dammit Potter..." He trailed off, giving Sirius a slight grin, and reached out to touch his friend's elbow. "What's wrong, Pads?"