As far as I know there are several easy things you could try. First of all: remember that this is a first draft. It doesn't have to be perfect. Just keep on writing. Once you have finished the first draft you can go and change everything. Sometimes taking the pressure of having to be perfect off your shoulders is enough to lift a writer's block. Take some time off from writing if you need it. After a good night's sleep your inspiration might return.

If you've done this and still don't know what to write, you could try to step into the shoes of your main character. Start writing about an ordinary day in his or her life, and soon your inspiration will return. When that happens you should think about what your character would do in the situations in your chapter. You shouldn't have any trouble coming up with things, if you can (almost) convince yourself that you're writing down a real situation with real people. Real people always react to the things around them in a certain way, and if you know your characters, you'll know what they'll do. And there you have a chapter.

Still having trouble? There is one more thing you could do, but you are not going to like it. A very effective (yet quite boring method) is to reread everything you've written so far. Change all the little (and bigger) things you don't like about it. Don't be afraid to remove huge parts, even whole chapters. This might add to the strength of your story. Maybe you'll even feel at some point that what your story or book really needs is an extra chapter. Just go wild. There is a reason after all that you were experiencing a writer's block. Most of the time it's because you've written something that doesn't belong in your story, or you've forgotten to add an important piece of information. In short, you know that your story isn't good enough yet, and your creativity blocks as a result of that.