It's definitely lens flare, from the chandelier in the upper right corner.
If you're using a filter, take it off for shots into the light like this, or try to keep the actual light source outside of the frame (and use a lens hood to keep the light off your lens).
You can also try a better filter. The cheap ones reflect a lot of light, and can make flare a lot worse. A good filter will have anti-reflective coatings that will help to reduce these kinds of problems (you should still take it off when shooting into bright lights, though; it will make it less obvious, but not eliminate it completely).