Three short lines, and almost nothing happens. The speaker simply notes that they need to buy eggs later on. It reads like a note scribbled on the back of a hand or a thought passing through someone's head while they're busy with something else.
That plainness is the point. The speaker doesn't seem excited or upset; the tone is flat, practical, a little tired, perhaps. The word "must" gives the thought a small push of obligation, yet "later on" lets it drift off into the vague future. So the feeling is mild duty mixed with easy postponement.
The mood is quiet and ordinary. By setting such a tiny chore in a poem, the text suggests that everyday life is mostly made of these small, unremarkable thoughts. The poem doesn't tell us what else is going on in the speaker's day, and that gap invites us to wonder. Is this calm routine, or a small anchor of normality while bigger things sit unspoken? The poem leaves that open.