NullReferenceExeption when trying to put GameObject into an Array

Hello! I am currently working on a 2D TopDown Survival game, and need some help.

To get the Tile GameObject for doing stuff like digging, I save all tiles of my current chunk into an array.

For example: Tile-198-7 (Numbers are x and y positions) are saved in an array by position. This Tile would be saved in myArray[198,7].

When I try to put my tile into that array, I get that Error here:

NullReferenceException: A null value was found where an object instance was required. TerrainManagerScirpt.loadTileInArray (UnityEngine.GameObject tile, Int32 xPos, Int32 yPos) (at Assets/Scripts/Terrain/TerrainManagerScirpt.cs:44) Tiles.createTile (Int32 x, Int32 y, Int32 intTileType, UnityEngine.Sprite sprite, Int32 offset) (at Assets/Scripts/Terrain/Tiles.cs:23) TerrainManagerScirpt.Start () (at Assets/Scripts/Terrain/TerrainManagerScirpt.cs:31)

Down below are my scripts. Thanks!

Tiles

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class Tiles
 {
     //not used for now, Tile ID
     int tileID;
     //The Tile object
     GameObject objectTile;
     //Tile Sprite
     Sprite tileSprite;
     public Vector3 tilePos;
     TerrainManagerScirpt terrainMan;
     //Creates the TileObject. Uses position, what Tile it is, and the sprite used. (Tile type is only 
     //for reference, is not used to decide the Sprite. This is the job of the terrain Manager.
     public void createTile(int x, int y, int intTileID, Sprite sprite, int offset)
     {
         //Gets the TerrainManager
         GameObject terrainMan = GameObject.Find("TerrainManager");
         TerrainManagerScirpt terrainManager = terrainMan.GetComponent<TerrainManagerScirpt>();
         //Gives ID to Tile (for reference)
         tileID = intTileID;
         //creates the actual Tile. Tile has coordinates in its name
         objectTile = new GameObject("Tile-" + x + "-" + y);
         //sets offset
         objectTile.transform.position = new Vector3(x - offset, y - offset, 0);
 
         //Gives Position to Tile (for reference)
         tilePos = objectTile.transform.position;
 
 
 
 
         ////
         ////
         ////
         //This is where the GameObject is supposted to get saved into the array. It gives
         //The object to the loadTileArray funktion in my TerrainManager
         terrainManager.loadTileInArray(objectTile, (int)objectTile.transform.position.x, (int)objectTile.transform.position.y);
         renderTile(sprite);
 
     }
     //Renders Tile, adds SpriteRenderer and sets Sprite.
     public void renderTile(Sprite sprite)
     {
         tileSprite = sprite;
         objectTile.AddComponent<SpriteRenderer>();
         objectTile.GetComponent<SpriteRenderer>().sprite = tileSprite;
         }
 
 }

TerrainManagerScript

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class TerrainManagerScirpt : MonoBehaviour {
 
     //Saves all Sprites in an array
     public Sprite[] sprites;
     //Saves tiles in an array
     public GameObject[,] mapTiles;
 
     //Sets size of Map
     private int mapSize = 20;
     private int x;
     private int y;
     //sets offset, so map gets generated "around" the player
     private int offset;
 
     public int tileType;
 
     Tiles Tile;
 
     void Start() {
         //set Offset
         offset = mapSize / 2;
         //Create TileMap
         for (int x = 0; x < mapSize; x++)
         {
             for (int y = 0; y < mapSize; y++)
             {
                 Tile = new Tiles();
                 Tile.createTile(x, y, tileType, sprites[tileType], offset);
             }
         }
     }
 
     // Update is called once per frame
     void Update() {
 
     }
     //This is used to load tiles into my array (mapTiles)
     public void loadTileInArray(GameObject tile,int xPos, int yPos)
     {
         GameObject newTile = tile;
         mapTiles[xPos, yPos] = newTile;
     }
 
     
 }