Like people said just open it up and push everything back in place and clean it out a bit. I had the same R2 and L2 problem, just adjust the springs until it's springy again. Now my controller works like day 1 and I don't have the random button pushing problem anymore.
i once dropped my controller 3 times and after i picked it up after dropping it 3 times and every thing was fine.
i think the reasion your controller went out of controll after you droped it because it might be because you dropped it on carpit