Thanks for providing the additional information.
Looking at the video, the limp doesn't look all that bad to me, and it's likely he just tripped over something or got it caught in something, and sprained, or strained the leg. Nothing uncommon with heavyweight duck breeds.
You can give Ibuprofen, but if you do, he needs to be set in a pen that reduces his mobility because the ibuprofen will directly interfere with the way he perceives pain and may cause him to overuse the leg, and further damage it internally.
For the limp, you can administer some B vitamins for leg health, try soaking the leg in Epsom salt water, and if needed, move him into a pen that reduces his movement, and put padding inside. Generally, though, give them time, and they usually heal up fine. It's just a matter of time.
He seems quite healthy, I doubt he is suffering from an impacted crop. If you're concerned check his crop in the morning and pay attention to his feces, and feed/water intake.
