Nino doesn't remember much about what he did as the Bubbler but he remembers why he became the Bubbler in the first place. When Nino first met Adrien, he was dull, all his steps were precise, he never laughed, just gave a sad smile. He was quiet and reserved, while the most of the girls said it made him mysterious. The boys said it made him look depressed.
Nino knew it was it was up to him to bring Adrien out of his shell, it took a certain amount of time till Adrien was laughing and smiling everyday, so when he saw his efforts crushed by Adrien's father, he entered a deep rage. How dare Adrien's father make him miserable after all the effort it took to make Adrien happy.
When he came back to himself after becoming the bubbler it was bittersweet, his friends were back, most would laugh and joke about it, but at times he could see the flinches when he touched their shoulder, he could see the glares that some parents would send him while he walked to school.
Nino laughed and smiled like before only this time most of his smiles were fake, only Adrien remarked. He confronted him about it in an old classroom and asked him what was wrong.
After two tense minutes he finally admitted defeat and told him about what was troubling him, Adrien looked at him and smiled, he then rested his hand on his shoulder and said "You'll always be my best friend".
So when Adrien took him to lunch and sat on the same table as Marinette and Alya he didn't say anything, when Marinette looked him in the eye smiled and waved, his felt relief and when Alya took his hand and squeezed it under the table, his heart fluttered and by the looks the whole table, he knew he was smiling naturally. Nino wasn't perfect but his friends weren't either and he thanked heavens for that.