Late at night, just after midnight, the speaker is alone in a dark room and feeling unwell. The title, "sick," sets that up, and the stomach ache in the last stanza makes the discomfort physical. Then someone's voice arrives, probably over a call or messages, though the poem never says how. It fills the corners of the room, which suddenly feel less empty.
What the two of them talk about is nothing special: small talk, bad jokes, things they happen to have in common. The poem lists these plainly, almost like a shrug, and that is the point. The comfort comes from the ordinariness of the conversation, not from anything grand being said.
The final lines tell us what it meant. "Somehow" suggests the speaker is a little surprised that a person could ease the pain this way. The mood is quiet, intimate and tender, with a hint of the loneliness that made the voice matter so much. The speaker may be sick in body, but the poem suggests that being heard and accompanied is what actually helps.