If there is a concern for skin cancer especially melanoma, one should always be seen by a board-certified dermatologist for evaluation in person and shouldn't rely on a photo consultation.
That being said, there are other benign reasons for streaking of pigment in the nails that are more common, and pigmented lesions including moles can darken with hormonal changes of pregnancy as well as other things such as medications. Streaking of the nail is caused by pigmented cells in the nail matrix that then grow out into the nail plate. From what is visible in the photo, the streaks look uniform. Dermatologists will look for hutchinson's sign, widening of pigment at the base of the nail and irregular pigment under the cuticle in the nail matrix, as well as discuss your risk factors including family history and sun exposure.
Sunbungual melanomas (or melanomas of the nail unit) often present at a later stage since patients delay evaluation. I would recommend you see a dermatologist; and, if it looks benign in person and a nail biopsy is not recommended, a photo can be placed in your chart so it can be monitored over time.