What to tell your professor when they think you've plagiarized? It was an honest mistake; I put my sources in the paper without a ref.
I believe it was an honest mistake, but even without intent, it is still considered plagiarism. I hope your prof understands. Good luck.
Just tell him that you were reviewing your paper and you noticed that you forgot to cite a source, and dies he mind if you ammend your references.. Just tell him it was a mistake and what can you do to fix it
If that doesn't work ask your professor about taking an incomplete (and finish it as soon as possible.)