Lab 3 - Analog In&Out - Problem occured/Figured out

This is not my first time doing Analog In and Out. The potentiometer worked fine last time, but it didn't tonight no matter what I was testing around anything.
The problem was that LED didn't show delicate difference when rotating either potentiometer or flex sensor. It kept blinking in very same interval. Then I switched the power source from USB to A/C adaptor but same result was shown. Only reason that I can assume what caused this malfunctioning LED might be from the wood attaching process. Since the screws were about 3mm longer than the depth of wood piece, I had to grind them by using of disc grinder.
Did it somehow damage the board? Were those screws fasten too much?

Sensors I tried to sync:

• Potentiameter
• Flex Sensor
• Force Sensor

On arduino program, I could see numbers changing and they were not following given analog input. They even varied when the switch stopped.

__________________________________________________________________
Revised Sep 25th - It turns out, my board only works when doing Digital IO, not Analog IO.
Mouna helped me out enormously in thousand ways to figure out what caused this, we finally came up with the idea of 'partial damage' on my arduino board. So, I need to buy an extra board to explore deeper Analog world.