"Unity application is running" message

When I try to upload avatar in unity it says “Unity Application is running… Stop it to access the Control Panel” and I was wondering if this is supposed to happen and if so how long does it last and if not how do I get rid of it

When pressing “build” on the control panel it’ll compile the avatar and enter “play mode” in unity to load the upload screen. This is under the game tab. To stop this just press the play button at the top of the screen.