If infringement of a published work begins before the work has been registered, the copyright owner can obtain the ordinary remedies for copyright infringement (including injunctions, actual damages and lost profits, as well as impounding and disposition of infringing articles). However, the owner cannot obtain special remedies (statutory damages and attorney’s fees) unless registration was made before the infringement commenced or within three months after first publication of the work.
That's the problem. The publication already happened and the photo is a year old, so it's out-of-window for registration to obtain statutory damages and, at least as important, fees and costs, which are a huge problem since they come out of your recovery. Further, if it's a trade magazine or similar the meaningful sales all happen within days of release, so impounding of infringing copies is of little harm to the publisher.
This is why that "every 90 day" disk sent in for registration with all your new work, while it has a small cost and hassle associated with it, is well worth the trouble.