You don't need hundreds of sprites, you only need one TileMap.
It's not straightforward, but doable. Create different tiles for different situations -
1. dug (or digged ) tile and no other dug tiles around
2. dug tile and one dug tile next to it
3. dug tile and two dug tile next to it - on right and below
4. dug tile and two dug tile next to it - on left and right
5. dug tile and three dug tile next to it
6. dug tile and all tiles around also dug
7. grass tile
You can use these 7 tile types to form any kind of landscape.
When player digs a tile, check the state of neighboring tiles and select the correct tile type. Rotate it if required.
Then update the neighboring tiles the same way.