Burn smell from arduino uno I have did something stupid.. I connected 10K Ohm potentiometer at its maximum value PARALLEL with a LED. The positive long leg of the led to arduino 5v and the negative leg to the GND.
After giving arduino 5v from USB Mobile Charger ( Output: 5V , 1A ) I smelt a burn and quickly removed the charger from the outlet.
I waited a few hours and connected the arduino ( without any components ) to the charger again. and the arduino worked. I then connected it to the PC and uploaded the blink sketch of the on-board led and it worked !
Then I uploaded a sktech for blinking led on other pins and it worked also !

My question is:
1) What is damaged on the board ?
The smell is near the regulator but I'm not sure if it's from the regulator itself or just a component near it.

2) Can it be safe to still using the arduino board on USB Power or Battery Power without any problems ?
That burn is likely the smell of the potentiometer, not the arduino. I would check the arduino with a multimeter set to resistance to make sure that the Vin trace resistance is nominal.