I say let him think what he wants about him naming the puppy but AFTER you get him just keep calling the puppy the name that you've chosen. Since you'll be the one taking care of your puppy, the name should stick. I'm sure your boyfriend will fall in love with your little one once you get him. My husband said if I got a little dog that he wouldn't walk him (the only dog my husband said he was walking would be a Bulldog!)
After we got our puppy he fell in love with him too and now he argues about who the dog loves more!!!! I dress my dog, put his hair in a top knot, and guess who walks him now!!!! It'll all work out I'm sure. Have fun with your new puppy.