Raycasting in 2D is not working

So I am trying to check if a user has clicked an object in my 2d game. I am using a 2D knob sprite like the image below, and I have included a circle Collider 2D around the sprite.

This is my code,

     //If the left mouse button has been clicked
     if(Input.GetMouseButton(0))
     {
       RaycastHit2D hit = Physics2D.Raycast(Camera.main.ScreenToWorldPoint(Input.mousePosition), -Vector2.up);
 
       if(hit.collider != null && hit.transform.tag == "Dot")
         Debug.Log("Dot Hit");
     }

I'm not hitting the Debug.Log inside the inner if statement. Each of my sprite has the tag, Dot. I'm following it just as it says in the documentation. I've checked the mouse is getting clicked, and it does come inside the outer if statement.

EDIT: I tried Debug.Log ing the Camera.main.ScreenToWorldPoint(Input.mousePosition), and even though I am moving my mouse around and clicking randomly, the value that gets printed is always the same.