In Islam Allah (swt) is most-just, most-forgiving. (Partly as a non-Muslim, which I love to hear.)
This Hadith answers your question (bolded part in your reference):
On the authority of Ibn Abbas (may Allah be pleased with him), that
the Messenger of Allah (peace and blessings of Allah be upon him)
Verily Allah has pardoned [or been lenient with] for me my ummah:
their mistakes, their forgetfulness, and that which they have been
forced to do under duress. A hasan hadeeth related by Ibn Majah, and
al-Bayhaqee and others. - 40 Hadith Nawawi 39
According to Islamic scholars (I cannot cite, but I will ask my Muslim friend when I have the chance) you should repent make Tawbah and make a strong pledge to Allah (swt) you will try to avoid such incidents in the future.
Note: You have not sinned in Islam, Islam is very forgiving in the case of accidental sin.
When those come to thee who believe in Our signs, Say: "Peace be on
you: Your Lord hath inscribed for Himself (the rule of) mercy: verily,
if any of you did evil in ignorance, and thereafter repented, and
amend (his conduct), lo! He is Oft-forgiving, Most Merciful.
- [Qur'an 6:54]
Sin in Islam is classified as:
Sin is sin, but sin is punishable when one has knowingly committed sin. (Unknowingly they will not be forgiven, but when they find out what they did was sin, they must repent.)