In just three short lines, the poem sets two scenes side by side. In one, a woman sleeps, and her nose, the detail the speaker fixes on, looks young again. In the other, someone is playing cards late at night. The title tells us the sleeper is a gambler's wife, so the poem seems to be seen from the gambler's point of view, or at least from someone who is watching her.
The tenderness is easy to feel. Sleep smooths away the worries of the day and gives her back a youthful look, and the speaker notices it with real affection. But the last line pulls against that softness. The cards suggest the speaker is away from her, caught up in the habit that probably causes her strain. The poem doesn't say so outright, but the mood seems quietly guilty and wistful: he can see what he's missing, or what he may be costing her, and still the game goes on. Its calm surface holds a small ache.