If you're asking whether you are at risk of being prosecuted, I would suggest that the answer is no. You reported a crime to the proper party. If you feel compelled to do so, you could also report it to the authorities, but that may open up an entirely different bag of worms that you may not wish to deal with. Either way, your conduct as described would be difficult to criminalize so I think you can rest easy.
Posting an answer to your question does not create an attorney / client relationship such that you can or should rely on the information provided herein to take action. Instead, it is intended to simply provide you with information. I am not your lawyer and cannot provide you with legal advice unless and until I am hired to do so.
Criminal Intent is the issue here. Based upon your description of what you did I do not believe you would be found to have the requisite criminal intent to disseminate child pornography. You did exactly what should have been done and what is encouraged by the website.
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It shouldn't be a problem, but I wouldn't type anything that can be construed as an admission in that you copied and pasted illegal images. If you were being monitored, they are seeing this. You do not have an attorney-client privilege in these forums.