How to animate a change of sprite?

Hi guys, im really new in Unity2D and I'm making a videogame for Android. I have a character sprite working but i need to animate with my character pick another piece of the body (My character is a flower that have 3 petals) When she picks one petal, one light appears covering the actual sprite and then the light disappear showing the sprite with 2 petals. I will post some pics of my actual character with her 3 states.

Thansk a LOT.

 

you can use the built in animator tool for animations, plenty of tutorials on how to use it

if its just replacing the image, you can edit the SpriteRenderer.sprite with the new sprite