May be, You shouldn’t  put input and labels to  torch.autograd.Variable because  autograd is handle by default and also Variable is depreciated now. inputs are already changed to tensor by transforms, so need not to worry that.
you have this error RuntimeError: Given groups=1, weight of size [6, 1, 5, 5], expected input[100, 3, 224, 224] to have 1 channels, but got 3 channels instead
that means your input should take (3,224,224) but you may be passing 256