It is quite possible to check your opponent with two knights. However, it is not possible to checkmate your opponent unless they purposely throw the game. Check is just an attack on the king, while checkmate wins you the game. And also, I saw you have an online game in this position. In the future, don't ask for advice about your games until they are finished.
checkmate with 2 knights
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When I say throw the game, I don't mean resign. I mean the opponent has to make about four specific moves in a row to allow the checkmate. It can't be forced.
Frankly, the helpmate with K+N+N vs K would be too difficult for beginners to produce. As for more advanced players, the draw would be too obvious and play would not continue.
For example if beginners worked together to make the checkmate happen and reached the position after move 8, they would have to realize how to lose a move with a simple king triangulation.
Zer0velocity wrote:
In that case, how could the game continue if your statement is true, Arch?
Wouldn't it be an automatic draw if you can't checkmate with two knights and a king? And frankly, I think you can checkmate with two knights.
Technical term is "Helpmate", since perfect play by both sides will not lead to mate, but repetition. Two knights + king is generally understood to be a draw, unless you really have nothing better to do... 
Is it possible to check my opponent while I have 2 knights & king & he only has a king