Bronze develops a natural patina over time. Sometimes there’s an awkward adolescent phase… a piece starts out shiny but gets a fingerprint which stands out… but with a little patience or more handling, the bronze develops a natural patina which melds everything together.
If you want your shiny new baby back, I recommend Simichrome polish. You might want to wear gloves. Apply polish to a clean cloth and apply. Then use another clean cloth to buff clean. Works great!