Q:

How to decrypt using only ciphertext for NimbusDS?

I am using JWEObject(JWEHeader header, Payload payload) for encrypting. 
Is it possible to decrypt using only ciphertext? If so, how?

A:

No, you cannot decrypt the ciphertext without key. That is, not unless an implementation mistake has been made.
Jason web encryption seems to have been defined for modern algorithms such as RSA-OAEP and AES-GCM. Although none of these has been proven secure, it is generally assumed that they are by the cryptographic community.

