Noticed one of the pistons wasn't coming out as quick as the other on my XT brakes. Took the pads out and was trying to get them to come out evenly when I realized that I had pushed the one side out too far. Saw a tiny drop of fluid come past the piston, and when I tried to push it back in I had to use a lot of force before hearing it make a snap noise and then slide in normally.
It seems to be functioning normally now but I'm wondering if I trashed the caliper and should be buying a new one.
You'll be fine, except you might be in for a bleed as you most likely added air in the caliper. It's kinda hard to damage those piston seals to be honest.
Bleed the brake, lubricate the pistons again if need be, and you'll be good.
I also did the flick the lever thing to get air bubbles out and the next day the master cylinder was leaking. LoL can't win. Threw on my old deore rear brake and will probably buy hope when I have cash. Forget shimano.