Hi I got my Lamy 81 pen some time ago and I was messing with it and it found that it was a piston filler, now I want to refill it and clean it but it won’t open. I couldn’t exactly remember how I opened it but I did remember it was at the end that I opened it, I used my teeth to try twisting it open because my hands wouldn’t work and I heard something crack, I’m worried and I don’t know what to don’t can someone please help me?