You can use stairs at home, bottom step. Lower the heel of your non-working leg to the floor, tap it on the floor. Working leg pushes through the ball of the foot, keep heel slightly off the step.
Search Reverse Step Ups for a video demonstration. 1-3 sets of 10 -20 reps should be fine. This will help strengthen your patellar tendon, and can be therapeutic It'll increase blood-flow around the knee and that may aid in recovery,. You can also do this thing called flossing where you use something, like an ace bandage, to wrap your knee then do Reverse Step Ups, then take of the bandage. Should increase blood-flow and aid recovery once again.
If you have questions ask. Be careful, if it hurts too much don't do it. Let me know how it goes.
I'm not a medical professional, but you should see one asap if you can.