Can an individual sin and not know they have sinned? It can happen. So, the answer to the question is “Yes!”
“And the LORD spake unto Moses, saying, ‘If a soul commit a trespass, and sin through ignorance, in the holy things of the LORD; then he shall bring for his trespass unto the LORD a ram without blemish out of the flocks, with thy estimation by shekels of silver, after the shekel of the sanctuary, for a trespass offering: and he shall make amends for the harm that he hath done in the holy thing, and shall add the fifth part thereto, and give it unto the priest: and the priest shall make an atonement for him with the ram of the trespass offering, and it shall be forgiven him.'” Leviticus 5:14-16 (KJB)
I have never kept it secret that I am not particularly fond of the book of Leviticus. Partly because, maybe mostly because there is still too much of the old me, the old flesh that I am hanging on to. Father forgive me. In Your Spirit Lord I love all Your word.
Through the whole word, the whole counsel of God, yes, even Leviticus, I learn of my guilt, my shame, my sin; even the one’s I did ignorantly; and then I take them to the cross of Jesus, and realize that He took it away. The sacrifice that paid the debt of all sin was Jesus on the cross, dying a death of horrible rejection, unimaginable pain and agony, and He rose again from the grave.
It is not sin to be ignorant of something such as sin; but it would be to remain in that ignorance. Just a thought.