Hello Jessica! Thank you for your question. I am a licensed computer professional with over ten years of experience, and I will be assisting you today.I'm sorry about the issue. Please try the following:- Press & hold down both the Command and Option keys on the keyboard while opening (double-clicking) on the Aperture program, then it will give you three choices, then try each choice (from top to bottom) until it works.
If needed, please trash the file "aperture library.aplibrary" in your Pictures folder, then check.Please let me know if there is still any issue.
Edit: It looks like you are away; when you are available, please click on the Reply to Expert tab below and reply back to me, so I can help further as needed. Thank you very much.