How to deal with this kind of split in trim?

It seems like after I meticulously put up and glued the miters on trim pieces, I often end up spotting a nagging crack like this, usually somewhere on the window casing. I'm really hoping to avoid redoing this entire window, especially since I'm out of material right now. I even tried shooting a nail through the side to secure it, but I'm still worried it might crack further. How do you usually remedy these types of splits so they don't worsen? All your feedback, tips, and tricks are hugely appreciated! 🙏 #HomeImprovement #DIYFrustration #TrimWork #Carpentry #WoodWorking #CrackedTrim #HelpMeFixIt #HomeRepair #WindowCasing