How do I make a sprite clickable only if there isn't any another sprites above it?

In a 2d game where I have to dig from up to down destroing the sprites that i can reach from above

You can use the sprite object's 'is overlapping at offset' condition or the system 'is overlapping point' condition (and then compare pickedcount) to check if there is an object at the location specified (above) before allowing the action to destroy the sprite to run.