It's never a good idea to make up a lie. They will only get you in trouble. You made your offer and he said no. That's it, any deal that could have been is now dead unless you were to make another offer.

Given that he rejected your offer, there's nothing for you to worry about. Tell him that because he rejected your offer that you and he have no business and that he should stop contacting you. Remind him that he rejected your offer and therefore he has no grounds to file any kind of complaint against you.