Help needed to find the big mistake Below is a a game in which I played as black. A chess engine analysis told me that I made big one mistake. Can someone point out what it is?

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1. d4 b6 2. e4 Bb7 3. Nd2 g6 4. Bd3 Bg7 5. Ngf3 e6 6. O-O Ne7 7. Qe2 a6 8. Re1 d6 9. c3 Nd7 10. Nf1 h6 11. Ng3 b5 12. Bd2 Nb6 13. Rad1 Rb8 14. b4 Na4 15. Rb1 c5 16. e5 cxd4 17. cxd4 d5 18. Rec1 Rc8 19. Be1 h5 20. h4 Bh6 21. Bd2 Bxd2 22. Qxd2 Rxc1+ 23. Rxc1 Nc6 24. a3 Ne7 25. Qc2 Nc6 26. Bxg6 fxg6 27. Qxg6+ Kd7 28. Qg7+ Kc8 29. Ng5 Qf8 30. Qxf8+ Rxf8 31. Nxe6 Rf7 32. Ne2 Nb2 33. Ng5 Nd3
There's more than one mistake in this game, but the biggest one is the last move: 33...Nd3. Probably this is the mistake that was pointed out. It allows White to win a piece (e.g., 34.Rxc6+ Bxc6 35.Nxf7). A better move would have been moving the rook away with 33...Rf5.