At almost 55 years old, I do not like running at all. But use couple races a year to motivate myself to exercise.
Like many have said, if you have a serious injury, please allow it to fully recover first.
In my very first full marathon training, I had a grade 2 calf pull. I would run after 2 weeks of rest. Then the pain would come back. Finally, I had to stop all exercises using legs and went for several a physical therapist treatments. So, instead of one months delay, it took over 3 months.
To most of us, the goal is to be able to run well into our 80s. Take care of injury is a key part of that. If something a permanently damaged, then you may be able to run any 5 ~ 6 years.