Too bad; hope it isn't serious.
But as I found out a couple of years ago, as we age, bone density declines, and some guys even develop osteoporosis. But we ALL lose bone density no matter how active we might be. And this bone loss also weakens the point where muscles attach to the bone.
In my case, I just dropped 18" off a platform, landed off-balance, and caused an avulsion (detachment) of my hamstring muscle up in my butt. It probably should have been surgically repaired, but my doc told me my bones were already too weak. As a result, my running times went from 9 min/mile to 15 min/mile and have stayed there. But fortunately without further pain.
There is a lot of literature
on the internet:
...Muscle strain is a common injury, especially in individuals who...fail to warm up sufficiently. Severe strains are a rupture of a tendon-bone attachment with separation of muscle fibers. Severe strains may require surgical repair....
I assume you didn't warm up before you stretched to reach that sock behind the dryer. :-)
You're a lot younger than I was when I was injured. So you should have more options. But I wouldn't depend only on your doctor's advice or an MRI report. I'd do some reading to try to analyze your situation yourself, and ask good questions. Good luck!