The white circle in the left top hand corner of my Android phone please tell me what it is now

[AC Question]

In the top left-hand corner of my phone is a round white circle that has never been there and I'll send it just appeared and I don't know what it's for can anyone tell me what it is and why I was there and then I asked the question of what it was and it went away but it's really confusing me I like to know if anybody knows what it was

 

[belodion]

What was its size? Was it a ring or a solid disc? Was it transparent?

 

[altobobcat]

The left hand space in the notification bar is usually for running apps. Installed any new apps recently?