Q:

What is this strange light in photo? 

I found a picture from my camera archive 2012, which I need explanation about.  It looks like either something happened to the camera or a certain light was captured. 

A:

It looks like a caustic, a shape that is produced by refraction of bright light at curved surfaces, most prominently when curved in more than one axis.  Glasses filled with a clear liquid frequently show such effects, but even an empty drinking glass or bowl can do so.  
To me it does not look like a lens flare at all.  Most importantly you can see the shape conform to the recesses in the wall or ceiling. 
Addendum: It might be produced by reflection from a strongly curved surface as well.