Looks like hard work to remove completely, but for starters I'd try selecting the green 'ball' with color-range, and make an adjustment-layer with hue-saturation (or curves), then with shifting the hue slightly into red and making it a bit darker, you should be able to lessen the effect. By fine-tuning the layer-mask you should be able to get a not to shabby result.
As 2m suggested, changing the coloring will probably be best. Due to the overexposed nature of the image there is not a lot of detail and it would be pretty tough to reconstruct the details with channel operations, selections and the clone stamp. Only the blue channel shows some of the underlying structure while the red and green have the blob, but at the same time the blue channels contrast is not good enough to prvide the textures so one could use blending modes to filter out the flare. Give it a warm color so it fits the mood and it should feel much less disturbing.
He wants to remove the lens flare. Just a matter of applying the
Clone Stamp Tool.
The result might be not convincing. but that's due to the mediocre
quality of the source.
Best regards --Gernot Hoffmann