It just looks like hyperpigmentation to me. The quality isn't the best but I wouldn't be surprised if you had a couple of shallow rolling scars. You can do acid peels (lactic, glycolic, etc.) at home to lighten pigmentation and you can use AHA cream, like Dan's AHA+. The cream you can use every night (but start slow) and peels probably twice a week and then you also slowly work up the percentage.
How long do you think it will take before it goes away completely?
It depends on the person - how long does it usually take scars to fade for you? If I get a scar anywhere, it usually takes me a year or more to fade, my skin just sucks like that -_-. You should see a difference in your skin within the first few weeks though, and you'll notice it constantly improving as you continue using it.