It is definitely a reflection in the lens system and its cover glass. This type of reflection, not true "optical flare", is common with very bright light sources and lenses covered with a flat filter or protective cover glass. The reflections will be 180 degrees from the light source and roughly the same distance from the center of the image as the light source.
When these occur with regular cameras that have a "protective UV filter" mounted the best fix is removing the filter. When that's not an option (e.g. not discovered until later, shot with a cell phone or tablet were the cover glass is permanently fixed) the fix is retouching.