As soon as John came down from his high, Sherlock removed his fingers, not wanting to overstimulate him.

Instead of pushing right in, which would almost definitely overstimulate him, Sherlock held him and kissed him, running his hand over his body until he had calmed down a bit. He knew that John didn't have the refractory period (or lack of) that he had, as a god, but he was patient, and he would wait until his lover was ready.