I found a solution.
To like post I've implemented a simple POST request using likes connection of facebook post id.
This is the code:
Request likeRequest = new Request(Session.getActiveSession(), fBPostId + "/likes", null, HttpMethod.POST, new Request.Callback() {
@Override
public void onCompleted(Response response) {
Log.i(TAG, response.toString());
}
});
Request.executeBatchAndWait(likeRequest);