Solitary Man

The film opens with 54-year-old Ben Kalmen (Michael Douglas), an attractive and very successful car dealer in the New York area, at his annual medical check-up; his doctor tells him he needs a CAT scan to get a better look at his heart, due to an "irregularity" in his EKG.
About six years later, Ben's fortunes have drastically changed. He is taking oral medications but never got the prescribed heart tests, and his lost sense of "immortality" has sent him on a self-destructive binge: habitual lying, sexual affairs, divorce, and bad business decisions that nearly put him in prison. He is broke, borrowing money from his daughter Susan (Jenna Fischer), and still unwilling to accept his age, ignoring his heart problem, and has a serial sexual appetite.
Ben, who cheated often on his wife Nancy Kalmen (Susan Sarandon), accompanies Allyson (Imogen Poots), the 18-year-old daughter of his girlfriend, Jordan Karsch (Mary-Louise Parker), to her college interview at a Boston college campus where Ben is an alumnus, having been a prominent donor during his more prosperous days.
On campus, Ben meets an impressionable student named Daniel (Jesse Eisenberg) who appreciates his wisdom and advice. Later that night, Ben and Allyson sleep together.
Back in New York, Ben expresses a desire to continue the relationship, which Allyson dismisses as a one time experiment with an older man - crossing "the Daddy" fantasy off her "list". Frustrated with Ben, Allyson flippantly tells her mother about the sexual encounter. Jordan breaks contact with Ben and withdraws the support Ben needs to open a new auto dealership. While discussing his overdue rent with his building manager (Lenny Venito), his daughter Susan appears and tells him he is no longer welcome in her family's life because of his inconsistency and unreliability as the grandfather of her son, after discovering an affair Ben had with her friend.
Facing eviction, Ben asks his college friend Jimmy Marino (Danny DeVito) to give him a job at his campus diner. Allyson, now a student, discovers Ben working near her. Ben receives a call from Jordan demanding he leave town immediately and threatening if he does not that she will have Allyson's father's connections persuade him to do so with physical force.
At a college party cruising, Ben recognizes a customer from the diner then makes a sexual advance toward Daniel's new girlfriend, Maureen (Olivia Thirlby). Shortly after the girl rebuffs him, he is severely beaten by an ex-police officer (Arthur J. Nascarella) who heads up Allyson's father's security team.
After discussing his view of life with Jimmy, Ben collapses and wakes up in a hospital with Susan at his bedside. Ben then leaves the hospital against medical advice. He apologizes to Daniel for his indiscretion and discovers Nancy on the bench where they met. Nancy has learned of Ben's medical condition and realizes that set the pattern of self-destructive behavior in motion. Ben tells Nancy that aging and the prospect of dying caused him to feel "invisible", so he decided to plunge into life with full gusto. She tells him that's no excuse, but she understands and offers him a ride back to New York City. The film ends with Nancy waiting in the car for his decision and a young woman walking by Ben, still sitting on the bench, in the opposite direction. Ben looks one way at Nancy, then the other way at the woman. The film ends with Ben standing and looking into the camera.

Question: Who does Ben apologize to for his indiscretion?
Answer: He apologizes to Daniel.