Falling asleep help!

My son, who will be seven months on the 15th, has learned how to pull himself up to a standing position. We have lowered his crib as far as it can go down but he’s mastered it so well he can use the slats to pull up, he doesn’t need the flat surface of the sides. Since learning this new skill about two, maybe three?, weeks ago he won’t fall asleep on his own anymore. He just wants to stand. He still sleeps through the night just fine and naps 1.5-2 hours at a time, I just cannot get him to fall asleep on his own! I’ve tried just letting him kind of play in his crib in hopes he’d fall asleep but the more tired he gets the harder time he has sitting back down from standing and he ends up falling and making himself even more upset so I end up just rocking him to sleep. Does anyone have advice for getting him to go back to falling asleep on his own? We’ve NEVER had a problem with him being dependent on us to sleep. He’s always been able to do it on his own until he learned how to stand.