Problem with dictionary inside of a class

Hello, I just began working with classes and I cant get variable Dictionary blocks to work. Whole script manages terrain generation. Im trying to create chunks and assign them to dictionary - that works, inside of that chunk there is another dictionary containing all the blocks of chunk - it just doesnt want to store newly created blocks in it. When Im trying to access specific block by:

GameObject tt = chunks[new Vector2(3,2)].blocks[new Vector2(3,2)];
Debug.Log(tt.transform.position);

It gives me this :/

KeyNotFoundException: The given key was not present in the dictionary. System.Collections.Generic.Dictionary`2[UnityEngine.Vector2,scrTerrainManager+chunk].get_Item (Vector2 key) (at /Users/builduser/buildslave/mono-runtime-and-classlibs/build/mcs/class/corlib/System.Collections.Generic/Dictionary.cs:150) scrTerrainManager.Start () (at Assets/Scripts/mapGenMoj/scrTerrainManager.cs:52)

Please help me Im almost total newb in that matter...

 using System;
 using System.Collections.Generic;
 using UnityEngine;
 using System.Collections;
 
 public class scrTerrainManager : MonoBehaviour 
 {
     public class chunk
     {
         //class variables
 
         public int chunkSize;
         public Dictionary<Vector2, GameObject> blocks = null;
             public chunk(int xPos, int zPos, int size)
             {
                 chunkSize = size;
                 blocks = new Dictionary<Vector2,GameObject>();
                 
                 GameObject chunk = new GameObject("chunk," + xPos + "," + zPos);
                 chunk.transform.position = new Vector3(xPos * chunkSize, 0, zPos * chunkSize);
 
                 for(int x = 0; x < chunkSize; x++)
                 {
                     for(int z = 0; z < chunkSize; z++)
                     {
                         GameObject cube = GameObject.CreatePrimitive(PrimitiveType.Cube) as GameObject;
                         cube.transform.parent = chunk.transform;
                         cube.transform.localPosition = new Vector3(x, 0, z);
                         GameObject tt = cube;
                         blocks[new Vector2(x, z)] = tt;
                     }
                 }
             }
     }
 
     public int mapSize = 5;                                                                     //how big is the square made of chunks
     public int chunkSize = 8;                                                                    //chunk size in blocks
 
     Dictionary<Vector2, chunk> chunks = new Dictionary<Vector2, chunk>();
 
     void Start () 
     {
         for(int x = -2; x < 3; x++)
         {
             for(int z = -2; z < 3; z++)
             {
                 //SpawnChunk(x, z, chunkSize);
                 chunks[new Vector2(x, z)] = new chunk(x, z, chunkSize);
             }
         }
             // this gives error every time
         GameObject tt = chunks[new Vector2(3,2)].blocks[new Vector2(3,2)];
         Debug.Log(tt.transform.position); // just debug thingy
     }
 
     chunk SpawnChunk (int x, int z, int size) // ignore it, obsolete 
     {
         chunk thisChunk = new chunk(x, z, size);
         return thisChunk;
         /*
         GameObject chunk = new GameObject("chunk," + x + "," + z);
         chunk.transform.position = new Vector3(x * chunkSize, 0, z * chunkSize);
         chunk.AddComponent<scrChunk>();
         chunks[new Vector2(x,z)] = chunk;
         */
     }
     void DeSpawnChunk()
     {
 
     }
     void Update () 
     {
         
     }
 }