If he really is nice, then he will not think you messaging him is weird at all. I always find when I message someone I don’t know well or they message me, that the conversations are the most interesting, and sometimes the deepest. You should try to get into a really great conversation with him. But don’t make your relationship with him rely on technology, start talking to him in person too so that it won’t be awkward in the future. So totally message him and then start talking to him just a little bit in person then gradually talk to him more and more. You could even wait for him to approach you first, but if doesn’t do that then you’ll need to take the initiative. Since you’re sort of in his group, he shouldn’t think it’s weird or awkward to be talking to you. Just take it slow. Good luck!