When I was almost 19,I committed a terrible sin and I regret it a lot,and I repented from this sin and didn’t return to it again..but Iam afraid that ALLAH will punish me for the sin I committed because its considered from the senior ones..and if the repentance was sincere from my heart will the sin stay with me...returning to the famous quote : As you sow, so will you reap?..
مجهول
And you have to avoid everything that reminds you of the sin and the sin wont stay with you and the quote doesn’t apply on you as long as you sincerely repented.