The way it works is that certain Fuzzies only accept certain jewels before they'll give you a riddle to solve. Then, if you solve the riddle correctly, you get another jewel to give to another Fuzzie in exchange for another riddle, and so on.
However, not all of the jewels are in Fuzzieland. In addition to the one behind the brick, there's one in another film. So you'll have to leave Fuzzieland to find it.
Hope that's enough to get you going again!