Hi - chance you had what I had, which I was convinced was a pulled glute but turned out it was a damaged hamstring tendon (hence feels like its in your bum) ... but the area is quite complicated (lots of diff muscles in there so worth getting a physio opinion).
For me the pain was extremely bad for a week then died down but never went away and would flare up from exercise.
What I have and am still doing to sort:
No lunges/squats/deadlifts/stretching the hamstring
Hamstring bridges to work the hamstring without causing the tendon stress (so lie on back with legs raised on something, knees slightly bent and raise pelvis off the floor .... something like 7 times with ten seconds rest, every day if poss)
You may want to back off running after the race for a bit. I dont think a sports massage can help.
I'm off running atm due to some post marathon issues, doing lots of spin classes instead. The change is great and also by the time I'm allowed to run again (hopefully next week) I will be looking forward to it and it wont feel like a chore. Looking forward to doing more speed work.
I had knee and ankle problems until I added squats and lunges to my program. Suffered a hamstring injury so had to stop doing them to recover and started having shin splint issues due to my glutes not being strong enough and of my knees slightly turning in when i ran to compensate.
I cant condone weights more, but dont go overboard.