Nginx usses rong php-fpm

i have ubuntu18.4, nginx and php7.2 instaled on a rock pi 4 sbc.
i installed nextcloud. and opened firefox and pointed it to
and a get a 502 bad gateway.

nginx error log:
2019/12/23 22:03:49 [crit] 5047#5047: *1 connect() to unix:/run/php/php7.3-fpm.sock failed (2: No such file or directory)…

i think the problem is php7.3-fpm because i have php7.2-fpm up and running

$ service php7.2-fpm status
● php7.2-fpm.service - The PHP 7.2 FastCGI Process Manager
Loaded: loaded (/lib/systemd/system/php7.2-fpm.service; enabled; vendor preset: enabled)
Active: active (running) since Mon 2019-12-23 18:06:03 UTC; 4h 13min ago
Docs: man:php-fpm7.2(8)
Main PID: 3586 (php-fpm7.2)
Status: “Processes active: 0, idle: 2, Requests: 0, slow: 0, Traffic: 0req/sec”
Tasks: 3 (limit: 4572)
CGroup: /system.slice/php7.2-fpm.service
├─3586 php-fpm: master process (/etc/php/7.2/fpm/php-fpm.conf)
├─3588 php-fpm: pool www
└─3589 php-fpm: pool www

how do i correct this?
i am a old geezer doing this to learn something, and i think that i need some serious hand holding some help would be greatly appreciated
greetings bert

find the according nginx-configuration files with

grep -Rnw '/etc/nginx/' -e 'php7\.3-fpm\.sock'

and in those files change php7.3-fpm.sock to php7.2-fpm.sock

thank you Bernie_o for the moment i cant ssh in to my server, because in a other briliant move i installed a ftp server before installing nextcloud and made it work over ssh, and now my server tells me its the only service it can serve over ssh. i think i now Wat’s rong, the only thing is that i don’t have a hdmi monitor, so i cant log in directly. and for that i have to go to my son who already thinks i’m crazy for setting up my own server box.but its an other good reason to go visit him tomorrow.
I’m going to bed in a view minutes so i wil analyze your command “grep -Rnw ‘/etc/nginx/’ -e 'php7.3-fpm.sock” tomorrow, it looks like a real efficient way to go thru configuration files, i’m not great at bash but doing is a great way of learning, although a bit frustrating some times.
have a great night. greetings bert