Submitter of "image requests" deviates from agreement... now what?

I recently received an image request via this site and was more than happy to accommodate the user's needs. He wanted to use an image for his business website. I was in the middle of a host of other projects so rather than add to my already hectic schedule and drag out the process, I simply offered a reduced size of the image for use on the condition that a "photo by line" accompany the image. He agreed. Well, I visited his site and the image is used twice (on two different pages) and neither includes a "photo by line." Anyone have any suggestions? My wife is an attorney but I'd hate to drag this out down that road.

I would give him three options:

1 - Take down the images

2 - Add the 'photo by line' as per your agreement

3 - Sent him a bill for its use. Prices here

Thanks for the reply. I think I will do exactly as you have outlined but also include a time frame. I don't want to be a jerk about it. I thought I'd be nice to help a start-up company but my generosity is being taken advantage of. Lesson learned. Thanks again.