Use of hard bumpers can cause dental injuries. Anyone who has had a broken tooth knows how hard it would be to carry anything if your teeth are bad. Regular exams for fractured or discolored teeth should be done.
Abrasions and lacerations may happen in the field or in the water on "something" submerged. If bleeding is intense (not just a slow ooze) and the hole is over an inch long, or if the depth penetrates into the muscle layer, veterinary attention is necessary. Immediately, though, apply pressure to stop the bleeding, or if it is oozing, wash it with CLEAN water and blot with a CLEAN towel. If all you have is muck and mud, just wait. Also, a dog mouth, though cleaner than ours, is not helpful past the initial 3-minute lick. Don't allow excessive licking.
All aside, any dog that is worked should be on a joint support supplement, as research has proven that use of these BEFORE an injury substantially improves the outcome.