apra, there was no need for Dutta to know anything about Nakku. Because the situation in which he met her, she was the needful and he completely helped her. Later when she saved his and his friends life, understanding their situation and the danger to their life for saving DSP, he decided to keep them along with him.
Since Nakku started develpoing feeling for Dutta, she took the first step of understanding him with out letting Dutta know her feelings. This boldness of hers impressed Dutta to consider her worthy enough to be his friend. But still the bonding was not so strong because of the presence of Supriya. Dutta always thought that he was changing his behaviour for making Supriya comfortable rather than thinking that why he accepted Nakku's advice. Also when Nakku was projected as Supriya's ally in her elopement, Dutta was hurt by Nakku's involvement because he started to consider her as his friend.
So unless Nakku's importance in his life or his feelings for her are cleared, he will never try to understand her.