I understand how you felt, but honestly, you did what you needed to do! If he judges you for it, that's HIS problem. In hindsight, I suppose you could have said something about being full and feeling bad for not being able to finish it all... but oh well! If you go out again you'll eventually order something you can eat more of, or take leftovers home. He won't always think you're a picky eater
I hope this works out for you! The start of new relationships/dating are always so fun/nerve wrecking etc.!