Musicians are often temperamental. Just generally, I would suggest inviting him, and if he refuses, just happily go on and practice alone. Have you ever noticed that when you are watching someone play a violin, especially a song that you know, you get a feeling of wanting to play too? So like you said, you don’t want to nag, but you want to play. You don’t need him to be playing too. Just play and maybe he’ll join in. Meanwhile, you’re improving your skills. He’ll notice.
Let music be your experience. You’ll attract playing partners when you are fully immersed in the process of learning. Allow him to not have the same passion, but don’t let it hinder yours.