Can't upload. Same error everytime

Everything was going fine and I was able to upload sketches to my atmega 328P MC. However, randomly today I get this error the first time I try to upload a sketch,

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

i'm using the right com port and under tools and boards, I made sure I switched it to Arduino Uno since my teacher at school said that it was pre-programmed to be and Uno. Is this an error meaning that my board is fried? Or, is it a simple fix where I just need to reset something? Note that the previous program still runs, and when I press the reset button, it does reset the program. The only ISSUE is UPLOADING anything new. I tried different computers etc. None of my classmates have this.

Did you try to reburn the boot loaded by accident?