Hi,
Your image dimension is 3xMxN. To use imshow, the image dimension should be (M,N,3) if the image data is 3 dimensional. In addition the values should be in range [0,1] or [0,255]. In your case, it looks like that the values fall in the latter range. Hence, no issues with the pixel values. But, you still have to transpose. Following would be a solution.
import matplotlib.pyplot as plt
import numpy as np

npimg = img.numpy() # img is your tensor
plt.imshow(np.transpose(npimg, (1, 2, 0)))
plt.show()

Thanks