This is most likely lens flare/ghosting, not dirt on the lens. Bright light sources—like the chandelier visible in your updated image—can reflect between lens elements and sometimes between the lens and a front filter, creating colored spots or repeated shapes in the photo.

How to reduce it:

• Remove any UV/protection filter when shooting into bright lights; filters often make flare worse.
• Use a lens hood to block stray light.
• Recompose so the bright light source is out of the frame, if possible.
• If you do use a filter, a better multi-coated one can reduce reflections, though it won’t eliminate flare completely.

So yes, this is a normal optical artifact when shooting with strong backlighting or bright lights near the frame.