Re: MCL, meniscus, mmmmm!
I had about the same injury last fall. I have much the same symptoms, stiffness when first standing, and that same pain that seems to be worse when laying down. Dr diagnosed it as either a severe sprain or small tear in the medial meniscus and said rest Ice Ibuprofen and time. It actually has woke me up in the middle of the night some times. Bracing helps when I need to be on my feet for a long time. Ice is a major help. Being very mindful of how I move, especially when pivoting on that leg which is how the injury occurred.
I think the biggest help for me is having my chiropractor realign it on a regular basis. That brings the most relief.