Which JetPack version are you on? Do you have python symbolically linked to a different python version than python 2.7?
If you want to try installing PyTorch+torchvision manually, you can find the PyTorch wheels and instructions here: https://forums.developer.nvidia.com/t/pytorch-for-jetson-nano-version-1-5-0-now-available/
This message from your screenshot I haven’t seen before: Defaulting to user installation because normal site-packages is not writeable
Is it possible that the permissions of that dir have been changed or corrupted somehow?