Knight on B4

Anybody has any idea how to deal with it? Of course I can move pawn but it will hold development of pieces.

Usually when the opponent neglects opening principles (e.g. not developing pieces, moving the same piece twice in the opening, attacking by itself without coordination from other pieces and so on), the answer is usually to just continue piece development yourself. This way the opponent falls behind in piece development and you can use this advantage to counter attack later. 

This position is unique though. You can just ignore the silly move Black just made and grab the "extra" pawn with 4.Nxe5. A general rule of thumb is that a pawn is worth 3 tempi. After you snag the e5 pawn, your Knight will probably only use one other tempi to fall back to f3 and you keep the material advantage.