How we can go to the pari-nirvana if not by being a bodhisattva?

I had noticed something that seemed to me a contradiction. I would be grateful if someone could resolve for me this contradiction . To attain the state of pari-nirvana you need to liberate yourself from the lie of being a separate part of the universe, then the pari-nirvana through this prism seems to be an egoistic thing since you exit yourself from the samsara but you leave the other existences in samsara.Which seem the epitome of egoism But the bodhisattva return to the world for helping the other existences which seem more altruistic and by this way more close to pari-nirvana. Therefore we get that going to pari-nirvana is in a certain sense a contradiction with being liberated from the lies ... I hope I am being clear... Thanks in advance !