yes of course not an elite runner, no coach or anything like that. but prize money from winning races is how i survive, so taking time off is not an option. even if there were no prize money, i am not the sort of person to not line up for a race I have entered. i will always go and worst case I have to DNF midrace if I feel like I am causing further injury to my body.
so how about the ibuprofen, is it a good idea as a one off, if the aim is to manage pain and get through the race? i have had other tendon problems before e.g. achilles, but that typically fades after a warmup and I don't feel it thereafter. This peroneal tendon seems to be pain that manifests after an hour of running and progressively gets worse - not something I have any experience with and not something I want to be dealing with an hour into a 10-hour run.