90% of injuries these days are caused by poor positions and postures. It is very rare that you will need to rest an injury and do nothing with it. For the majority of soft tissue injuries, rest is the worst thing you could do. Now, if you have a bone sticking out or your knee has done a full 360 degree twist, then yes, rest will be needed to start with. But, your best form of medicine, is movement! Movement will keep the blood flowing around the injured site and help keep it mobile. The biggest thing you need to do is work out WHY this injury happened in the first place. Normally is it something simple as how you sit in the car or how you reach for something at your desk. Create more awareness of your movement patterns in your everyday life as this will aid your training. You only spend 1, maybe 2 hours in the gym or exercising each day, where you will be moving well. It is the other hours outside of the gym that are more important as these are more repetitive than anything.
It is not hard to focus on form and function in the gym because that is exactly what you are training for. Also, most of the time, you will have another set of eyes on you, like a coach or a training partner. It is very rare that someone will enter the gym or go for a run and purposefully use bad form.
The most important hours are the ones outside of the gym because this is where the majority of humans become lazy and move just for the sake of it. They don't lift safely, they don't move with purpose, the just move! This is where most of your everyday habits get created and the body adapts to these positions and postures as that is where the brain believes you like to spend most of your time in!
Imagine sitting down at your desk ALL DAY LONG and then having to deadlift, squat, run, skip at the gym as soon as you finish!! Your body will be hating on you as all the preparation you have done for the session is sit down on your butt all day long!!
Yes, you have a warm up routine at the gym, but imagine if you actually used the rest of your day as your warm up gym!? Less time will be used in the gym to warm up, less time stretching and getting mobile.
Life is basically a warm up for the gym. You will actually lift more, run faster, stretch further if you paid more attention outside of the gym!
Just going to the gym and thinking that's all you need to do isn't going to get you far!