Be Humbled and See Why God is called Lord

And all the inhabitants of the earth are reputed as nothing: and He doeth according to his will in the army of heaven, and among the inhabitants of the earth: and none can stay his hand, or say unto Him, What doest thou? (Daniel 4:35 )

When I got saved the Church I ended up being baptised in had a sign outside reading Jesus is Lord. That scared me. What does this word mean. Its actually a good thing that he is sovereign over world and all the inhabitants of earth are reputed as nothing.