Here's another take....

The romance aspect of the carbon freezing scene was needed because it provided an opportunity for the "I know" line. Although the line was improvised (brilliantly) by Ford and Kershner, it was needed as a tension-breaker. It was one of the few laugh-out-loud moments in the film, during what was easily the film's most tense scene.

So, for that reason, it was needed.

Plays and movies have historically used "comic relief" to ease the audiences' anxiety (as well as dissipating any sense of heavy-handed melodrama).

The line also reinforced the narcissistic nature of Han's character, buffering any feeling that he was getting too selfless in his relationship to Leia.

A lot was accomplished with those two little words.