Tankie Molly

Hello everyone first post here I'm a bit stuck and also scare because i'm in valor montain i just beat up kyogre talk to Ember and co. then i find the red cristale kill the scientist by activivating it. But the problem is here, i've gone back on the entrace and realyse that i need rock smash to hit the pillar and continue my wonderful journey. So i came back to Terajuma to take my rock smash pokemon and go back to valor montain but now i can't activate the red christal so i don't know what to do plus I've saved the just after leaving Terajuma :'( Hope someone can solve this have a good day