@Neutral Name,
Chronic pain often hides other sections of the body that are also suffering, as our body can only deal with a certain amount of pain.
If his feet are cured, it's possible that now, the other problems associated are coming to light.
I don't think it is un-common to have injections to try to release inflamation and I suspect that is what occured. However, if your grandson actually has a nerve problem then only pain management as he has already gone through for his feet will help.
Here is the thing. He states that he is contemplating hiking for 6 months through Europe, so that shows determination.
He has beaten a portion of his illness (eventually) so that shows determination.
I doubt he is suicidal rather needs to blame everyone for his pain and I suspect the loss of his girlfriend.
It is my understanding if groin pain continues, then it is not from needles, rather he has a problem with nerves and needs yet again to see a Doctor .. and stop blaming you.