Thank you for all the replies,
I have changed the deepstream sink option as suggested by @Andrey1984, so now there is no window showing the inference from yolo.
I created a systemd service for the script to run it at time of boot,
as suggested over here ( Jetson nano auto run python code when power up - #3 by xuanthinh010110 )
the script runs but for some reason it do not start gnome terminal.
If I run the service as a user service then it do opens the gnome terminal and works fine but then it do not starts at boot time automatically.
systemctl --user enable mytest.service