2nd revision to fix saddle nose tip. Dent and line across nose. Do I need a 3rd revision? (photos)

Regardless of issue, 6 months is a bit early to consider another revision rhinoplasty. Without having seen your pre-operative photos, and without knowing how your dorsum was augmented, it's hard to say whether the horizontal line is something to be concerned with at this point in your healing. Follow up closely with your surgeon for now, and when fully healed if the line persists or worsens, then it would be appropriate to considering another surgery.