SMM 2:40pm Apr 10 2019
You are still early in the healing. Yes, at this stage elevating the leg as much as possible will likely help a great deal, and that means during sleep. If you can elevate as I described earlier, throughout the day, you may be able minimize discomfort. And if lucky, you'll actually end up sleeping for short periods during these times. Sleeping for more than a few hours at a time may be difficult yet for another few weeks.
And with no cast, do take care to elevate/make comfortable the thigh as well. That will rest soft tissues (muscles, tendons,etc) and rest the knee. I think I forgot to mention that the lower leg should be just above heart level, so elevation is about 4-6 inches.
I also found it hard to sleep on the back, but now prefer it. As you elevate the leg, make sure your neck is comfortable, so select pillow that will keep the head comfortable. I also found putting a pillows around the sides (hip/rib cage) kept me in a comfortable position.
Hope to hear in the near future that things are getting better and better.
PS...yes, I think it is a bad idea to rest/elevate the leg on hard surfaces.