First, the good news: your photos are automatically protected by copyright the moment they were created. Under the Copyright Act (17 U.S.C. § 102), copyright attaches to original works of authorship upon creation. You do not need to register to own the copyright or to file a DMCA takedown.
However, registration with the U.S. Copyright Office matters if you want to pursue a lawsuit. Under 17 U.S.C. § 412, you can only recover statutory damages (up to $150,000 per work for willful infringement) and attorney's fees if the work was registered before the infringement began, or within three months of first publication. Otherwise, you're limited to actual damages and profits.
For your immediate situation, here are your options on Amazon:
- Amazon Brand Registry — if you're enrolled, you can file an IP complaint directly through the Brand Registry portal. This is the fastest path to removal.
- Amazon's Report a Violation tool — even without Brand Registry, you can report copyright infringement through Amazon's standard reporting process.
- DMCA takedown notice — you can send a formal DMCA notice under 17 U.S.C. § 512(c) to Amazon's designated DMCA agent. Amazon must "expeditiously" remove the infringing content upon receiving a valid notice.
I'd recommend all three simultaneously, and also registering your photos with the Copyright Office now (— it costs about $65 for a group of photos and takes 3-6 months). For more background on IP enforcement, see /Demand-Letters/IP-Content/.