Small gaps after braces!! I took off my braces about three weeks ago. There was no gap before I had braces. (photos)

I wear my retainer 7/24 for the past three weeks but the gap is still there.I went back to my orthodontist to check yesterday. He told me it's just the stain and he polished it. He also used the floss to test it and told me my teeth are already in contact...but I can still see a small gap!! I can't see the gap after i put the retainer on, I don't know if the retainer close the gap or it's the plastic hide the gap. Will the retainer close the gap if i keep wearing it? What can i do??