The speaker notices a small glitch: because of an imperfection in her eyeglasses, a tiny second star appears beside Venus, low and to the right. To her, it looks like the planet's hand curled into a slightly raised fist. Instead of being annoyed by the distortion, she plays with it.
In the second stanza she imagines what kind of fist this would be. It isn't a threatening one, but a soft Tai Chi fist, powerful because it is balanced and calm. Venus, standing for love and beauty, smiles lazily, relaxed and unbothered. Hate and ugliness become a "nattering nuisance," a foolish enemy that has no idea how strong she is.
The mood is gentle, amused, and quietly confident. The speaker turns a flaw in her vision into a small act of imagination, and in doing so she suggests that love and beauty don't need to fight hard to win. They simply need to stay steady.