Sherlock let John clean himself off, then Sherlock cleaned himself, working around his arse and legs extra well, he was still leaking some of that Demon come out of his hole.

When he was done, he toweled himself off, and wrapped his arms around John, holding him while he came up from his headspace and back to the world while Sherlock told him that he loved him and that he did a good job and that he was safe and it was time to come home again.