Russia currently provides Germany with about 40% of its hydrocarbon energy sources—oil and gas. The Nord Stream pipeline was originally intended to provide something like 55 billion cubic metres of gas to Germany. If you're an energy expert, you'll know what that means. I wouldn't consider myself an energy expert, so I can't tell you what that means, but it sounds like an awful lot of gas.
The pipeline can always be turned on in the future. You can suspend exports and say you're not going to take them. That's always an option, if things change. That does give you, I think, important leverage vis-à-vis Putin's regime. It does mean that in the short term, he won't get paid for anything.