destory object not variable

think im getting my wires crossed when storing and destroying objects.

get this error:

MissingReferenceException: The object of type 'GameObject' has been destroyed but you are still trying to access it. Your script should either check if it is null or you should not destroy the object. grid.objGridSize () (at Assets/scripts/grid.cs:119) grid.hit (System.String hitObjString) (at Assets/scripts/grid.cs:109) grid.Update () (at Assets/scripts/grid.cs:80)

from this:

 // Something has been hit
     public void hit(String hitObjString){
 
         GameObject hitTile = GameObject.Find(hitObjString);
         storePosition hitPos = hitTile.GetComponent<storePosition>();
 
         if( hitTile.tag == "tile"){
             objGrid[hitPos.x,hitPos.y] = nullTile;
 
             Destroy(hitTile);
         }
         }