Satori is considered a "first step" or embarkation toward nirvana:

Ch'an expressions refer to enlightenment as "seeing your self-nature". But even this is not enough. After seeing your self-nature, you need to deepen your experience even further and bring it into maturation. You should have enlightenment experience again and again and support them with continuous practice. Even though Ch'an says that at the time of enlightenment, your outlook is the same as of the Buddha, you are not yet a full Buddha.