Sherlock is used to offending people.
He's not used to this.
He thought he could handle always asserting himself—thought that was okay—he was always right, anyway—so why didn't everyone just agree with him? But he learns with the slam of the door and John's quick footsteps down the stairs, that maybe he is wrong.
And it shocks him that what churns his stomach, sickening him to the core, isn't the fact he is wrong.
It's that he has offended.
(He thought he was used to it. He doesn't think so anymore.)
He sits there and feels sick and doesn't move because if he does, he doesn't know if it will all come up or stay down. (He didn't mean to hurt him; didn't mean to use authority in that context—yet this conviction strikes him as strange because he has never had the problem of telling someone how and what they should think before. They've all been idiots, anyway.)
It hurts. It hurts, and he doesn't know how to soothe the ache other than the inevitable (the admittance, the confession, the apology)—but if he submitted to that, would he be groveling, he wonders? How low would that put him?
It isn't until John returns home that Sherlock stands for the first time in five hours. It isn't until he sees his flatmate's blue eyes free of that angry, offended cloud that something in the Consulting Detective settles and stills. Yet even so, he finds his lips moving, utterings words that he had previously forbidden.
"…I should not have…said that."
It is the closest he can get to an apology—to facing that monster inside that is pride and selfishness and conceit and vain superiority—but John, good John, smiles just a little anyway.
"S'okay, Sherlock. You're just human."
(And he knows that such a thing is not an excuse or a pardon—but a reason to tame that bad inside. Humanity, fickle transport that it may be, is an enabler—imperfection at its base with the ability to get better. It does not justify; it prompts.)
For the first time in his life, Sherlock decides he can accept that he still has stairs yet to climb.
Crystal's Notes: Inspired by angsty events of my own today. xD; Long story short: I wasn't the one in John's position. I, actually, found myself in the position of the grievous offender-and it's a rather horrible business, really. So I had to apologize and get through that icky-sicky gut-churn that is guilt and remorse, much like Sherlock. In order to help relieve myself of the nasty thoughts that plague me whenever something like this happens, I decided to write.
(Writing's always a great way of venting, isn't it?)
Hope you've enjoyed.