Just call him Bijoy. We have a wonderful tradition of "official" Bangla nicknames unrelated to the official name, and should use those. Let us be proud of what we are this way, rather than attempting the deplorable "English Medium" hipness we see so often everywhere.
My nickname is Shubho BTW. I'd love to know everyone else's in this forum.
"And do not curse those who call on other than GOD, lest they blaspheme and curse GOD, out of ignorance. We have adorned the works of every group in their eyes. Ultimately, they return to their Lord, then He informs them of everything they had done." (Qur'an 6:108)