A scab in a straight line on your lip that suddenly appears without pain, itching, tingling, or burning could be due to various reasons. It's not possible to determine definitively whether it is HSV1 (herpes simplex virus type 1) or caused by trauma based solely on the appearance of a scab.

If you are concerned about herpes (HSV1), it would be best to consult with a healthcare provider for an accurate diagnosis. They can perform tests if needed and provide appropriate guidance.

In the meantime, keep the area clean and avoid picking at the scab to prevent infection and promote healing. If any symptoms develop or persist, seek medical advice promptly for further evaluation.