About usb camera use in jetson nano

Please check if you can run python sample like this:
V4l2src using OpenCV Gstreamer is not working in Jetson Xavier NX - #3 by DaneLLL

You would need to run v4l2-ctl --list-formats-ext to get detail of supported formats, and set width, height, framerate, format according to the source. Please refer to
Jetson Nano FAQ
[Q: I have a USB camera. How can I launch it on Jetson Nano?]