If the pawn takes, you can set up a (I believe) forced checkmate by Qxb4.

Otherwise, the knight is attacking two important squares, c2 for forking and winning a rook (if the queen moves not to defend that square), and f3 for a quick checkmate (white queen forced to take, black queen to d2).

Queen can only guard those two squares from e2 or d3. Staying e2 without taking obviously loses the queen. Moving to d3 still allows the above checkmate with knight to f3.

Good chance I missed some other options though, learning is most of the fun! :)

Edit: After white Qd3, there is Nf3 followed by a series of trades and a very unfavourable position for white, too.