The speaker's days and nights have flipped. Morning, when most people are waking up, is now when they sleep, and the poem treats that reversal as a quiet shock. "I saw rest I never saw before" suggests a new, almost startled relationship with sleep, as if rest were something the speaker had never really looked at until now.
The strangest and most telling line is "the bed I call Nurse." The bed becomes a caretaker, something that tends to the speaker. That hints at tiredness, or perhaps recovery, though the poem never says why the schedule changed. Judging by the wording, the speaker may be working nights or simply worn down.
The last line, "and I lease the room," adds a note of impermanence. Nothing is owned here; even the space for rest is borrowed. The mood is hushed, weary, and a little detached, with a dry humor running underneath. The brevity of the poem mirrors the small, enclosed world the speaker has retreated into.