I was testing the blink exemple in arduino, but I made a mistake when I put the ground of the blink in the Aref, instead of puting GND pin. I would like knowing if there is some problem
If you look at Fig 28-1 of the 328P datasheet, you can see that AREF is one of several sources that can be used as an input into the ADC circuit.
If you ground Aref, and select another source to use with Aref, then you would ground out that source.
That might cause high current draw thru the Mux to the right of where AVCC and the Internal bandgap parts, and the MOSFET to the right of the mux.
Or those parts may have limited current enough to prevent any damage.
Does your chip feel warm or hot to the touch? If so, something have been damaged.
If not, the parts may have survived.
Undo the Aref connection to Gnd for sure.
Not quit sure what you did, if it was the second leg of the LED in series with the resistor you put in Aref. then there should be no damage.
I agree with GijKieken, that should not cause any damage to Aref.