I changed, but i get the same error:(.
I change my code like this:
class SkullCNN(nn.Module):
    def __init__(self):
        super(SkullCNN, self).__init__()
        self.conv1 = nn.Sequential(
            nn.Conv2d(1, 32, 4, 2, 0),
            nn.BatchNorm2d(32),
            nn.ReLU()
        )
        #...


The images I trying process look like this:

And i get the same error:
---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
<ipython-input-174-15d7d37170f1> in <module>()
      9 #         print(images[0].shape)
     10 
---> 11         out = model(images)
     12         loss = criterion(out, labels)
     13 

6 frames
/usr/local/lib/python3.6/dist-packages/torch/nn/modules/conv.py in _conv_forward(self, input, weight)
    348                             _pair(0), self.dilation, self.groups)
    349         return F.conv2d(input, weight, self.bias, self.stride,
--> 350                         self.padding, self.dilation, self.groups)
    351 
    352     def forward(self, input):

RuntimeError: Given groups=1, weight of size [32, 3, 4, 4], expected input[64, 1, 32, 32] to have 3 channels, but got 1 channels instead