I agree that the song is about someone close to Pete that he hates, but I think the "ugly inner child" line is explaining that this person acts as a child and can't act like an adult about things. The title "jawbreaker" explains that this person upsets him so much that he grinds his teeth. This person always shoots Pete bad looks: "I caught your evil eye." The bad blood they have between them seems to stem from this person not siding with Pete on something: "Are you part of them, Or part of me," but either way this person is an annoyance to both parties: "Cause you bother them, And you bother me."
I agree that the song is about someone close to Pete that he hates, but I think the "ugly inner child" line is explaining that this person acts as a child and can't act like an adult about things. The title "jawbreaker" explains that this person upsets him so much that he grinds his teeth. This person always shoots Pete bad looks: "I caught your evil eye." The bad blood they have between them seems to stem from this person not siding with Pete on something: "Are you part of them, Or part of me," but either way this person is an annoyance to both parties: "Cause you bother them, And you bother me."