"I have a nice boyfriend."
Translation:Tengo un novio simpático.
I think bonito/a can be used to mean "nice" more in the sense of appearances than personalities. "Tengo un novio bonito" would be taken to mean physically attractive, not necessarily kind or pleasant to be around.
I just answered a question where bonito described a teacher, I got the answer wrong because it wanted me to say nice. When I use bonito here to describe the boyfriend as nice it's wrong. I am seriously confused.