Don't panic. I doubt very much if you have damaged anything. My guess is that the piston is sticking on the disintegrated buffer washer and a grotty o ring on the piston head.
Can you push the piston back in? This sometimes loosens things up a bit so that when you drift (good word that) it again it comes a bit further out.
Also, a squirt of a 'lubricant'(WD40 maybe)) will do no harm both from the rear, applied around the piston body and from the front via the transfer port. Let the lube penetrate before 'drifting' again.
Cheers, Phil