No, unfortunately you can't. If you arrive from Turkey to one of the Greek islands, you have to stay there, until the Greek authorities officially allow you to leave the island. This is called a "geographical restriction" and is part of the deal that was made between the EU and Turkey. If you manage to travel illegally to the mainland, the vast majority of people are not allowed to proceed their asylum claim there. You are either forced to travel back or you stay in a limbo on the mainland, without any progress in your procedure. The only way to continue your asylum procedure, is to return back to the island you have the geographical restriction on. Unfortunately in general the Greek authorities are really strict in applying this rule. Only in some very rare cases it is possible to lift the geographical restriction. But this process is extremely complicated and there must be very exceptional circumstances. Therefore currently in almost all cases, if you have a geographical restriction and want to continue the asylum procedure, it is better to comply with the restriction and stay on the island until you are officially allowed to leave.