Satan always wanted God's position in the "sides of the north" which was
above all else. However, now he has been reduced to the throne of Hell which is beneath everything and has power over none. "While" is important because Satan has said that he is tormented inwardly, but the other angels do not see this and they adore him. This means that he is putting on an act for them by looking tough on the outside. However, his regret and pain on the inside may make him a less effective leader. Satan boosts his image by trying to make himself look strong for enduring all this pain and not letting his followers see it.
This makes reference to Satan being the king of Hell. We tend to think of
kings as powerful and respected beings, but Satan is neither of these. He has no
actual power, and those who follow him are worthless because they are not
respected. Milton may be making a comment on the state of affairs in England.
The beheading of Charles
I brought to light the fact that kings are not all powerful. If Satan can be
king with no power and little respect what does that say about the rulers of
England? This reflects the change in people's attitudes towards the monarchy, in
that they no longer have the same aura about them.