Back in 1982...I had my worst injury. I was out close to a year with illiotibial band syndrome...at least that's what they called it. I rested and rested and rested and absolutely nothing happened. What's really strange is that the injury switched from one knee to the other without me really doing anything. Weird. I saw all kinds of medical personnel and they always prescribed rest. Finally, I saw Dr Phil Maffetone. After one week, I was back running. After a month I was at 70 miles a week.
Dr Maffetone helped me get a few bones unstuck and a few muscles activated...but he also gave me advice that no one else gave me. He wanted me to start running immediately. He did not want we running to the point of pain...but it was fine to be sore, have some discomfort ans seemingly aggravate the injury. He explain that you need to keep asking the body to get better and that muscles will basically "turn off" if you don't use them.
Since then...I have always implemented an active approach to injury recovery. I can't tell you how many little "niggles" I've worked around simply by slowing down...or using a combination of walking and running, ....or walking on a treadmill at an incline...and so on. I should also add that I never use aspirin or drugs of any kind and always try to get to the root of the problem.
It seems that there may even be some research supporting this method of coming back from injury...as described in this article. The research does not suggest that one should ignore injury and bull through as if nothing is wrong. However, it does suggest that mild pain is OK and gives some guidelines to follow.
One of the good things about training through an injury...provided you are sensible...is that you keep most of your fitness...so that when you do get your injury sorted out, you do not have a long period of trying to rebuild your fitness levels.
If you happen to have a setback, don't let it throw you. Stay calm and unwavering. Just do what you can. Keep giving your body a bit of motion...whatever it can reasonably handle. It needs that.