Ah, bless him, sounds like he might be a bit out of sorts after the holiday and getting used to your new home? I think imagination really ramps up around this age.
I try to just keep taking my DS back to his room when he comes out. If he is upset and needing comfort and finding it hard to settle, I talk him through going back to sleep. So I sit near to him and in a gentle voice say, "lie down, close your eyes, deep breaths" and repeat. I try to move back and out the room before he's fully asleep.
If your DS is needing this comfort, it might help to do more of a gradual withdrawal approach e.g. Start with something like those sleepy phrases until he is asleep, then another night only until calm, then another night just saying it once or twice before going out, then finally another night just getting to tucking him back into bed.