Strange noise when holding MacBook Pro
I had a problem where is sounded like a "click" when pressing on the area you described. This was quite annoying while typing.

To resolve this I added a little bit of sewing oil to the screws and edges of the case where it makes the noise.


Press on the area where it does make a sound
Add a little drop of sewing oil (not too much) to the screws and edges
Press a few times times. 
Wipe it the excesses and check if the noise is gone