[Sherlock actually wants to be less gentle. He wants for there to be a roughness to all this. When he imagined it (and yes, he had imagined it before, though they were just idle, glancing thoughts that meandered back away from sex very quickly like the very idea was too hot to touch) he assumed the entire affair would have all the sharpness and sting of a riding crop on the skin. Those were the associations his mind had made.]

[The tricky thing here is his inexperience. He doesn't want this to be gentle, but going in full force when you have no idea what you're doing seems the sort of thing that would lead to awkwardness and discomfort.]

[But it's awkward as it is, isn't it.]

I don't--hmm.

[He looks distinctly embarrassed now.]

My knowledge base is...limited in regards to this.

[It may seem like he's backing off again, but that's not the case.]

If anything I try doesn't work for you, tell me what to do instead.

[And with that, he finally abandons the last of those inhibitions, he clamps his mouth firmly around her nipple, and now there's teeth. He doesn't bite down too hard, but there's definitely some nibbling going on.]