Show texture or delete shader of a circle area on click

Hi everyone,

I am trying to show an area of the screen on click like a circle. I have uploaded a very simple image to show what I mean.. but I am having trouble to do so, I have tried playing around with shaders but the onclick just changes the whole texture back to normal...

Just to explain the image, when someone clicks the section of the cube it will reveal the texture as shown above. it is a 3d world but shown in a 2d plane, so if someone clicks the edge of the cube the other side will be colored as well. So I thought about just making a canvas but wouldn't look smooth.

If there is anyone that can help me with this that would be great either shaders, canvas or anything.

Thanks in advance.