L button stuck and won't spring back up?

The L button is just.. always down on its leftmost edge. If I hit my R button, it presses down and springs back up as normal. My L? It just depresses down and doesn't spring back up. Very annoying, as I'm trying to play the new pokemon super mystery dungeon game and L opens the attack screen. :'(

So right now it's as if L is always being pressed down. I can manually push it back up, but it's quite annoying have to press it down then push it back up when I wanna just tap it, you know what I mean? xp

I've tried blowing into it and even blowing compressed air around the button and brushing a tooth brush around the sides of it, but ... made no difference whatsoever?