This cheek kiss happens so early in the manga, compared to the anime. In the anime, the cheek kiss is in
an after-credits scene at the end of season 1, after the cultural festival arc. It also happens after Senpai finishes a drawing of a napping Nagatoro, but in a sitting, rather than lying down pose.
Side note: the events at the start of the manga are also shuffled around a lot in the anime. This chapter "should" be at the start of episode 3, but it's at the end of episode 4, mixed with some later chapter (or maybe original content, I don't know yet).