Depends on if stopping puts you or someone else in harms way. Sometimes you cannot stopp you can go a little farther pull over and call the accident in.
I was making a turn and a sportbiker was hotdoggin around the corner and hit a patch of gravel. Went flying. I could not believe my eyes when I saw cars just go around him. I stopped in the middle of the road to stop traffic and he could not believe some woman was stopping to help him. The ambulance got there and he asked about his bike, and I said don't worry I'll see it gets the the shop.
I have had several people stop even when I was just pulled over to catch my breath, so I would definitely stop for anyone on a bike.