Which means he's either in a nightmare or still in that strange universe where nothing has happened yet. He feels very sluggish and drowsy which means that something is interfering with his magic flow.
He tries to sit up and barely manages to before he realizes that there is someone in the room, more specifically on his legs. He freaks out a bit before he realizes that it's Pap, Or more specifically Pap before everything, he's even sleeping. He starts to cry, and another person walks in before he can full out cry. He wipes his eves with his arms and realizes that one is in a cast, and his jacket is gone. He feels the weight on his legs lift and he snaps his head up and sees Gaster holding Pap.
He looks at Gaster as he smiles at Sans softly and pulled the blanket back over his shoulders, then he leaves the room. As soon as Gaster leaves Sans burst into tears and cries until sleep overtakes him.