Formal:
* Witaj, moja miłości. (This is a very formal way to address your love.)
Informal:
* Cześć, kochanie! (This is a more common and informal way to say "hello my love.")
* Witaj, skarbie! (This is a more affectionate way to say "hello my love.")
* Cześć, moja miłości. (This is a more intimate way to say "hello my love.")
Other options:
* Witaj, mój/moja. (This means "hello, my [dear]")
* Witaj, kochanie. (This is a more affectionate way to say "hello, darling.")
Important note: The choice of words depends on your relationship with the person you are talking to. If you are unsure, it is always best to err on the side of formality.