No, not really. Smugness is being pleased with oneself for doing something which has harmful implications for someone else, but not at all for you. You know, like when the teacher's pet gets you into trouble for something she suggested, and knows that you will never be believed if you tell the teacher that she suggested it. That look on her face is smug.
I don't know if there is an opposite to smugness. Maybe the feeling you have when you do something good, and yet you know that nobody will believe that it was you that did it.
In any case, it isn't modesty.
The opposite of the word 'smug' is 'humble'.
He is not smug. He is modest.
The opposite of arrogant is humble or modest.
Modest is the usual opposite of narcissistic.
modest
The opposite (for a person) would be immodest. To a great degree, it would be arrogant or boastful.The opposite of modest (for other uses) could be substantial or great (a modest inheritance). For a home, the opposite could be large, palatial, or opulent.
Modest.
Modest ,
Modest, you dumbas$
The opposite of big-headed is humble or modest.
the opposite of pride (to be proud) is humility (to be humble).
Perhaps "humble".