It seems there is an
nginx.pid file with wrong contents, could you take a look at it? It is located in the following path:
It should not exist if Nginx is not running, you can check whether it is running with the following command:
ps aux | grep nginx
If it is running, just stop it with
kill PID, where PID is the PID of the process.
If Nginx is not running, and the file exists, just delete it and try again.
I hope it helps!