Arjuna and the other Pandavas went to heaven. Their presence in hell was just a test by Indra to test Yudhisthir.
Arjuna had committed a sin. He killed Bheesma and Karna by forgery. Yes both sins were on the instruction of God but a sin is a sin. He had broken the norms of the war. Arjuna started the misconduct.
Here is why each Pandava fell on their pedestrian journey to heaven.
The first to fall was Draupadi, she was imperfect because she preferred Arjuna over her other husbands.Then it was Sahadeva, imperfect because he was smug about his knowledge. Followed by Nakula, imperfect because he was arrogant about his good looks.Then fell Arjuna, imperfect because he was always jealous of other archers.And then, Bhima, imperfect because he was a glutton.
Reference: Mahaprastanika Parva