I posted this question on Doom emacs #help 's discord, and someone suggested to use: projectile-after-switch-project-hook
I'm not sure if I can place it inside my dir-locals.el, that hook could be evaluated before reading dir-locals and if I'm correct nothing would happen so.
Anyway, those are good starting points, I will take a look and if I find a solution, come back here to let you know.

Thank you, I will take a look at direnv. The idea is to run the command once indeed. I know there is hooks when switching project, but how to use them here is out of my knowledge.