Solved. I attached the popover to NSWindow view and used NSMouseLocation for popover's position.
NSPoint mouseLoc2 = [self.window mouseLocationOutsideOfEventStream];
NSRect r4 = NSMakeRect(mouseLoc2.x -10, mouseLoc2.y -10, 16, 16);
[self.myPopOver showRelativeToRect:r4
ofView:self.window.contentView
preferredEdge:NSMaxYEdge];