Was the knight a trap? What other blunders were made during the course of the game?
Hi MetalFactor. The opening ECO is E61 for the savvy ones that could comment on that. 17. O-O? bad move. The black bishop on f5 is pointing at the Queen, so the advance of the black pawn on e4 discovers the attack not only of the bishop on the Queen but also of the black pawn on the white bishop at d2; this is called discovered attack and it is lethal because it is double. Better was 17. Nxe4. At your level it is often recomended to do a lot of tactics not only for you to play them on your opponent but also for you to prevent them from happening to you. Got to keep an eye on the maneuvers of the fellow accross the board! Cheers.
I think 22. bxc5 was also a bad move. You should watch out when and how you exchange material.
Try computer analysis! It's really helpful and indepth (although it sometimes has some weird bugs).
16.Bxe4 is bad. Giving up your white square bishop just emphasizes the weaknesses on your kingside. 17.O-O is bad as your know. 17. Nxe4 is probably tactically sound but once again, your white squares are awfully weak. Best was proabably 16. Nxe4