Tattoos are a "get at your own risk" type of thing, meaning that you know it could possibly come out this way before you get it. That does not at all mean that this is your fault.
You can try talking to him. He will more than likely not give you a refund (after all, he had to use ink and other supplies to tattoo you), and he will more than likely not help you with removal. He might offer to try and fix it for you for free or low cost.
If you dont want it to be fixed, it may be in your best interest to just go ahead and pay for it to be removed. After its removed, if you feel you want it done again, take your business to another tattoo artist.
Always remember in the future -- if you are not happy with the way something looks on paper, you will more than likely not be happy with the way it looks on your skin. If you dont like the way it looks, tell the tattoo artist! Never get something that you are not sure if you are going to be happy with or not. If he says there is no way to re-size it, either dont get the tattoo or take your idea to someone else.