I am pretty sure knight + king checkmate versus a lone king is IMPOSSIBLE.
However, that was not the case of your game : you did not have a lone king, but a king + pawn. In that case, depending on the position, it's possible to checkmate as your pawn might block an escape route for your king.
Here is an example : lichess.org/editor/8/8/8/8/8/6N1/5K1p/7k_w_KQkq_-
Can you show us your game ?