Excuse me, all....
I see no reason to jump all over the OP like this. She did not hit the dog, her boyfriend did. And it seems to me that he did so out of ignorance, not malice. And furthermore, she came to Chaz asking for help. It amazes me that some members of this board can be so patient and understanding with a dog who makes a mistake, but will just rip apart a poster who does the same thing.
So, to answer your question....
Your pup can get over this, but you have to regain its trust. Be very gentle, and do absolutely nothing to hurt your puppy. Don't even raise your voice. It will take time to get over, but it is possible.
Do NOT ever hit your pup again. That will definately ruin any relationship with your pup. It will make him fearful, shy, and he may gain fear aggression issues. Be sure your boyfriend understands that.