Chosen Solution
Clicking noise in the lower right corner inside my Late 2013 MacBook Pro with Retina Disply. This machine has SSD so no Hard Drive to make a noise. It just started that last week.
Can you make a recording of the sound so we can hear it? I would suspect the fan is going on you. Review this IFIXIT guide: MacBook Pro 13" Retina Display Late 2013 Fan Replacement.
