Without personally examining you, take this with a grain of salt… however, it might actually be helpful to have the injection, especially knowing that you have an MRI to document the specific problem. I doubt it would be harmful unless repeated multiple times (as far as making the tendon weaker), although I do agree with taking it easy for about 2 weeks following.
It sounds from your description like you might have some sort of tendonitis or possibly a bursitis, both of which are common indications for corticosteroid injection. The injection itself may be difficult to hit the right spot, especially since I’m not sure what you mean by “high hamstring.”
Alternatively, you could try NSAIDs (ibuprofen or naproxen) for some time to try to reduce inflammation, assuming there are no reasons you couldn’t take them. In most cases, I would say the side effects from NSAIDs are greater than in injection, but this is a case by case basis.
In either case, rest is probably needed, and I doubt “work[ing] through it” would do anything but delay recovery, but again, I haven’t examined you myself.
If you are questioning the diagnosis or treatment, consider a second opinion from a sports medicine specialist.
I have a suggestion to get a cortisone injection in my high hamstring. It has been limiting me for 6 months. It is not a sharp pain, but it is definitely a pain there and I have not deadlifted in 6 months. It is horrid.
However, the doc says that the MRI shows no tear, just some inflammation. However, I am scared of the cortisone injection. Does anyone have experience with one? How long after one can you do nothing? The doc said 2 weeks???
Do they actually help heal it or do they make the tendon weaker? I had one once in my ankle and it just hurt more after I got the injection. (I later got surgery on the ankle)
If the injury is not a tear, purely inflammation can I just work through the pain and as I get stronger will it just go away? The pain isn’t severe, just enough to make me notice it and be scared that I’m doing more damage if I try to dead…
Thanks so much!