wget https://nvidia.box.com/shared/static/p57jwntv436lfrd78inwl7iml6p13fzh.whl -O torch-1.8.0-cp36-cp36m-linux_aarch64.whl -O torch-1.9.0-cp36-cp36m-linux_aarch64.whl
sudo apt-get install python3-pip libopenblas-base libopenmpi-dev 
pip3 install Cython
pip3 install numpy torch-1.9.0-cp36-cp36m-linux_aarch64.whl

To download and install torchvision 0.10 on Nano, run the commands below:
https://drive.google.com/uc?id=1tU6YlPjrP605j4z8PMnqwCSoP6sSC91Z
pip3 install torchvision-0.10.0a0+300a8a4-cp36-cp36m-linux_aarch64.whl

After the steps above, run this to confirm:
$ pip3 list|grep torch
torch (1.9.0)
torchvision (0.10.0)

You can also use the docker image described in the section Using Jetson Inference (which also has PyTorch and torchvision installed), to skip the manual steps above.
The official YOLOv5 repo is used to run the PyTorch YOLOv5 model on Jetson Nano. After logging in to Jetson Nano, follow the steps below: