Already checked and doctor found nothing to worry about. so could it be a scrotum cyst in the left side? with no pain and not always felt.

May be...: The concerned bump could be just a benign epidermal inclusion cyst. If painless and not hurting, indeed just leave it alone and don't squeeze and play with it. Meanwhile, collect the specific feature, degree, ; progress of the bump over time with its sequence of events, and bring them to doctor for review, analysis, history, physicals, and tests as needed so he/she may deduce what it's ; how to.