Four short lines, and the speaker packs a lot of hurt into them. They are talking to someone who has caused them pain and who now seems to feel a flicker of discomfort whenever they see it. The speaker names that feeling for what it is: guilt. "That little sting" is a small, almost dismissive phrase, as if the other person's discomfort is minor next to what the speaker has gone through.
The word "hun" is the odd, interesting touch. It sounds affectionate, but here it reads as sarcastic, a mock-sweet tone that sharpens the accusation. The last line, "and you caused that," is blunt and flat, with no room for argument. The mood is bitter and cold, with a quiet anger under it. The speaker doesn't shout or plead. They simply point out the truth and leave the other person to sit with it, which makes the poem feel both controlled and quietly cutting.