Well, there's really no such thing as writer's block. Really, you just took a wrong turn in your story and just need to go back and find a different direction. If you can't think of a story in the first place, here's an idea: Pick any object in the room. Anything. Pretend it's completely strange to you. Ask yourself questions about it. Let's suppose the object chosen is a house plant.
- Where would this kind of plant grow? A jungle? The neighbor's lawn?
- What might it be used for? Magic, perhaps?
And from even just those simple questions, you can come up with a story. The plant grows on the neighbor's lawn and the neighbor uses the plant for magic - What kind of magic? Why? Is the plant just part of certain spells, or is it the source of their magic? The plant grows in the jungle - describe the jungle. Is this plant the last of its kind? Is something destroying the plants? Why are the plants important? What does the destruction of the plants mean for the jungle? Perhaps it means more than loss of habitat . . . perhaps its destruction heralds the arrival of a dark force . . .
Hope this helped!