This is very difficult. One thing when you should consider stopping is if the pain becomes chronic and never goes away. I remember seeing a lot of top fighters pretty much living on pain killers. That's probably a clear sign you should stop.

I got a lot of benefit from doing intense martial arts when I was younger but sometimes I wish I had been smarter and not just ignored pain. But again, it's a difficult decision. Some things make you tougher and some things cause problems later on.