Lens flare refers to a phenomenon wherein light is scattered or flared in a lens system, often in response to a bright light, producing an undesirable effect on the image.
In order to create this effect, I referred to John chapman’s Lens flare which is not physically-based model. Of course, Physically-based Lens flare can generate more accurate effects but it is much expensive. To do this, it needs several independent effects ghosts, halo, diffraction created by very bright Scene color. And, at the final stage, composite the all effects with dirtmask texture and star burst texture (you can make it easily with a Photoshop tutorial).
<Dirt Mask Texture>
<Star Burst Texture>