Nicknames in a relationship

So me and my boyfriend have been dating for a while now. His name is Manuel (man-well) but everyone calls him Manny. Some time ago I talked to him about a new nickname that I can call him. Something for just him and me. I thought of whale and thought it was so cute but he said no cause his ex called him that. It's been like 2-3 years since they've broken up and I don't think it's fair to me to not have a nickname for him. Just last week was his birthday and she said happy birthday with a whale emoji. Can I call him whale or should I not?