you don't need anti inflammatory injections, at the most ibuprofen for immediate acute pain relief.
I did one of mine last year 6 weeks before a 40 mile race. I managed to rehab sufficiently to come in 13th in that, would have been top ten, pushing top 5 otherwise - lots of hard work required. Your September race should be fine, but you may not be entirely sypmtom free by then
My advice having doen this is that you do need to seek some professional advice, I would go to a sports injury therapist who specialises in rehab and getting you back racing again.
What you need to understand right now is hte degree of damage and the site of the damage. This sounds like chronic inflammation, but it could be concentrated at various points along the tendon, or the tendon sheath. WHat the sports injury therapist will do is assess immediate damage, short term rehab, any underlying causes (tight hams, calves in my case) and help you deal with that as well.
Where are you located as I know people in London, Lincoln, Cambridge, all of whom are part of a network that grows through word of mouth and all are excellent.