Informal:
* Moje małe aniołku: This is the most common and literal translation.
* Moje maleństwo: This translates to "my little one" and is a more affectionate term.
* Moje słodkie aniołeczko: This means "my sweet little angel" and adds a touch of sweetness.
Formal:
* Mój mały aniołku: This is a more formal version of "moje małe aniołku".
* Moje drogie dziecko: This means "my dear child" and is a more respectful way to address someone.
Note: The word "aniołek" (little angel) is often used in a playful or affectionate way, even for adults.
Ultimately, the best way to say "my little angel" in Polish depends on your relationship with the person you are speaking to and the tone you want to convey.