Thanks, looks like my class indices aren’t in the range as specfied. I printed the minimum and maximum values of my label for few iterations and this is what I got:

tensor(1) tensor(33008)
tensor(0) tensor(33004)
tensor(0) tensor(33001)
tensor(0) tensor(33003)
tensor(1) tensor(33003)
tensor(0) tensor(33001)
tensor(1) tensor(33000)
tensor(1) tensor(33000)
tensor(0) tensor(33003)
tensor(0) tensor(33000)
tensor(0) tensor(33007)
tensor(0) tensor(33005)
tensor(0) tensor(33004)
tensor(0) tensor(33006)
tensor(0) tensor(33000)
tensor(0) tensor(33001)
tensor(0) tensor(33000)
tensor(0) tensor(33005)
tensor(1) tensor(33001)
tensor(0) tensor(33002)
tensor(0) tensor(33001)
tensor(0) tensor(33002)
tensor(0) tensor(33000)
tensor(0) tensor(33001)
tensor(1) tensor(33000)
tensor(1) tensor(33000)
tensor(0) tensor(33000)
tensor(0) tensor(33003)
tensor(0) tensor(33006)
tensor(0) tensor(33002)
tensor(1) tensor(33002)
tensor(1) tensor(33005)
tensor(0) tensor(33002)
tensor(1) tensor(33000)
tensor(1) tensor(33000)
tensor(0) tensor(33003)
tensor(1) tensor(33006)
tensor(1) tensor(33000)
tensor(1) tensor(27000)
tensor(1) tensor(33003)
tensor(1) tensor(33001)
tensor(0) tensor(33002)
tensor(0) tensor(33000)
tensor(1) tensor(33002)
tensor(0) tensor(33000)
tensor(1) tensor(33001)
tensor(0) tensor(33002)
tensor(1) tensor(33001)
tensor(0) tensor(33005)
tensor(0) tensor(33004)

How do I tackle this now?