I broke my clavicle in Aikido during a forward roll about 3 months ago. Because it was a pretty bad break, I opted for the surgery (so now I have a metal plate and 7 screws in there). I was back on the mat about 2 weeks after the surgery, but only to help teach kid's class. I wore the sling and did not take any falls or anything. Because I was already a Shodan when this happened, I was able to help teach where I could, thus enabling me to still feel a part of things without putting myself in danger. I did all of my physical therapy, and about 2 months after the surgery I was back doing technique and taking soft falls (but not rolls). I only did this after getting clearance from my doctor. At this point I am doing as much Aikido as I can, minus the rolling. I have another 3 months before my doctor wants me doing that. But, I listen to my body and if I think a receiving a certain technique is too dangerous, I won't do it.
My advise would be: Listen to your doctors. Listen to your body. And when you are ready, immerse slowly back into Aikido. Adjust slowly to being back, don't jump right into breakfalls (which at the moment still make me feel a little shaky, but I'll cross that road when it is time).
And remember: It can happen to anyone, no matter how good you think your ukemi is, no matter how long or short you have been training. Injuries happen. And try to be positive about it. I got some really sweet X-ray photos out of the deal, and a sweet scar.