Your input contains 4 channels, while the first conv layer expects an input with 3 channels.
If you are dealing with RGB images, the 4th channel might be the alpha channel, which could just be removed.
If you are using a custom DataLoader, you could probably just use:
def __getitem__(self, index):
    img = Image.open(self.paths[index]).convert('RGB')
    ...
    # Alternatively remove the alpha channel from the tensor
    img = Image.open(self.paths[index])
    x = TF.to_tensor(img)
    x = x[:3]
    ...