they say you can't checkmate with only 1 knight, well .........................


They say you can't force checkmate with just a knight.
Your solution requires help from the opponent.
There exist no material with which you can't checkmate - given the right position. Any such generalization always refers to common positions as given by the Dark Knight!

Many smothered mates are done with the knight like that. But in the real chess world, nobody would not play Ka2 in that example which is a clear draw since a1 will be covered...
Right! K+B vs K is a draw. But as soon as your opponent has some extra units they can work against him and there is a potential (though mostly unlikely) checkmate.
There exist no material with which you can't checkmate - given the right position. ...
Lone king?
There exist no material with which you can't checkmate - given the right position. ...
Lone king?
Interpreted "material" as "besides the king" just as in the title of this topic!