Problem having uploading sketch to Arduino Uno

Hi guys. I was working on Arduino Uno. It was working completely fine. And then I tried to upload a new sketch to Uno and it gave me the following error.

avrdude: verification error, first mismatch at byte 0x0000
0x62 != 0x0c
avrdude: verification error; content mismatch
avrdude: verification error; content mismatch

I checked my board and port in IDE. It is selected correctly.

It does not matter which kind of sketch I tried to upload, It gives me the same error every time.

Could someone please let me know what is wrong with my Arduino Uno and how can I fix it?

Thank you in advance