@sabina - I've recently had to take 2 months off due to a knee injury as well. It is hard to get back into it with the fear of further injuring yourself!
I took up spin biking! That got me that cardio workout I was craving that I wasn't getting from running since I didn't want to make the injury worse. I made myself take it slow when I did start running again then I'd just spin bike and walk more since I couldn't do much running. It can be very frustrating but I also found it pretty cool to see my progress get better and now I'm running better than before my injury.
Hope you are able to find your motivation to get back out there!