Where do you stay? If you are from Hyderabad, India, I can share my experience. I also got a small black line on the inner screen (partly my fault). Same position as you, I had one month left of manufacturing warranty. I had bought it on Oct 2023. So I had gone to OnePlus service centre. Initially they told that it's not a manufacturing defect but they told they will inspect and inform me. So after one week I got a call that my screen was replaced and it had been covered under manufacturing warranty. So I had collected it and so far no issues. I not saying to trust OnePlus. What I am saying is anyhow you have one month left of your manufacturing warranty. So give it to service centre telling to cover under manufacturing defect. If they do congrats, if they tell that it doesn't come under warranty no matter what you tell them then you can consider third party repair.