It's lens flare.
Lens flare is caused by reflections at air gaps between glass elements inside the lens when one or more bright light sources are near or in the image frame.
Some people put a clear or UV filter on the front of their lens for 'protection', which adds an air gap to the lens giving lens flare an additional air gap where lens flare can be produced. If you use a filter for 'protection' you may want to remove it when you shoot scenes that have bright light sources in or near them.
Using a lens hood offer protection while also minimizing lens flare from bright light sources near the image frame. Once bright light sources are in the image frame, a lens hood becomes much less effective, if any, at controlling lens flare.
Filters added to a lens for 'protection' cause more problems than they prevent.