How I can make a b2Body in box2d so that it could form a ring which does not collide from the center just like a ring. like when we flick the object and there's another body (like pole), the pole can go inside from the ring.
I assume you want to view the scene from the side? Pretty easy to be done. Just create two circles that are connected to each others with some space in between:
You just draw the actual ring (the part not colliding) over the "empty" space.