How to get light out a photo on my iPhone 6?

I had VIP for a concert last week and on the picture there's a streak of light going across my face how do I remove it?

Correction: you can't "remove" it because there's nothing underneath it. You want to add detail where there's none. Print it large. Get an artist to paint in the area. Take a picture of it. Or try to do it in Photoshop, which would be harder because of the absence of control over fine detail. There's no magical way. The streak contains no pictorial data that can be recovered.

It depends on what is obscured by the unwanted streak and what there's to work with in the picture. There may even be potential donor material in any other pictures you took at the time. It's not possible to say for sure without seeing the image. If you upload it to an online gallery and post a link here then we can judge. You can also email me and I'll tell you what can be done.

You don't.

You keep it there. It's part of the concert atmosphere making the photo genuine and not appear as being manipulated.