Material is destroying sprite`s quality

Hi guys, I got a problem - I got a sprite of a castle in which i decided to do kinda torch light. I found out that it needs a shader, so i put a material on this sprite, and then there has shown some weird lines which are not drawn on a picture of castle. I send you picture of sprite with and without material( on top there is material and on bottom there is no material). I have drawn this blue lines to show you where the quality is being destroyed.

For everybody having the same problem. I found out that shader needs to be “Sprites/diffuse” and it`s working properly with light.