Did you read the verse...He does His will in the armies of heaven and amongst the inhabitants of the earth and none shall stay His hand. God answers to no one and no one can thwart His will. He is the LORD God omnipotent. He has no peers or rivals. This is what people were inferring when they said your god was too small. Your understanding of God renders Him less than He is.
Did you read the context of the verse? Does it say that Nebuchadnezzer was prophesying?
34 And at the end of the days
I Nebuchadnezzar lifted up mine eyes unto heaven, and mine understanding returned unto me, and I blessed the most High, and I praised and honoured him that liveth for ever, whose dominion is an everlasting dominion, and his kingdom is from generation to generation:
35 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?
36 At the same time my reason returned unto me; and for the glory of my kingdom, mine honour and brightness returned unto me; and my counsellors and my lords sought unto me; and I was established in my kingdom, and excellent majesty was added unto me.
37 Now I Nebuchadnezzar praise and extol and honour the King of heaven, all whose works are truth, and his ways judgment: and those that walk in pride he is able to abase.
Is everything everyone says about God in the Bible true and precise? The king was warned what would happen if he did not repent. It happened exactly as he was warned. As a king over avast empire who made decrees that were almost always carried out, what would he attribute to the God who imposed a predicted decreed penalty on him, the head of the empire? He would conclude -
35 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?
However, there are many times in scripture that God's decrees not carried out because men do not cooperate. In fact, Nebuchadnezzar himself had gone against God's decree to stop sinning. Saul went against God's decree and spared the best of the flocks and king Agag. Adam went against the decree of God and ate of the forbidden fruit.