I think your knee needs to heal more, especially after the added soreness of falling, so if it was me, I would wait for PT. How long? Well, I’m not in favor of formal PT in a facility, so I would say don’t even go. My PT caused me a lot of unnecessary set backs, and did nothing to actually help me recover. But, just because my experience was bad doesn’t mean everyone’s is. I would wait a couple of weeks, or more, before going, if you want to go.
Gentle movements would be just small bends, no pain, not even any discomfort, just bend a little bit to move the joint. As you heal, you’ll be able to gradually bend a little more.