The weird spot or visual disturbance you experience after looking at a bright spot, such as the sun, is called an afterimage. Afterimages occur due to the way our eyes and brain process visual information.
When you look at a bright object, such as the sun, the intense light stimulates the cells in your retina, which is the light-sensitive tissue at the back of your eye. These cells, called photoreceptors, become temporarily overstimulated. Specifically, there are two types of photoreceptor cells involved: cones and rods. Cones are responsible for color vision and function best in bright light, while rods are more sensitive to low-light conditions.
After staring at a bright light source for a prolonged period or if the light is exceptionally intense, the cones and rods become fatigued. When you then shift your gaze to a neutral background, the fatigued photoreceptor cells fail to respond adequately to the new visual input. As a result, you perceive a residual image of the bright spot, which appears as a negative afterimage.
The appearance of afterimages can vary. Typically, a bright spot will leave a corresponding dark spot in the afterimage, as the overstimulated cells need time to recover. The exact colors and duration of afterimages can vary based on individual factors and the intensity of the original stimulus.
Afterimages are generally harmless and tend to fade away within a few seconds or minutes as your photoreceptor cells recover from their fatigue. If you frequently experience persistent or unusual visual disturbances, it's recommended to consult with an eye care professional for a thorough evaluation.