For missing yesterday though, I offer you this useful trinket:
Did you know that the body can absorb some types of fishing line? It's true. Some doctors will use it for stitches because they don't have to be removed. So if your characters are out fishing and one of them gets a deep gash well...they could sew it up quite conveniently. Except for the whole infection thing.
For infection there are a few natural cures that could help. Garlic, though not readily available in the wild, does work as an antiseptic. So if your chars brought some to put on their fish their set.
But wait! He's bleeding too heavily. What do they do now? Well...you need an astringent. Something to help the muscles swell and close up. The one I'm most familiar with is yarrow. Some people know it because you can chew on the roots to numb your mouth. But its also an astringent and a decent bug repellent (decent not brilliant). Chew on the root for a toothache. Shove a leaf up your nose for a bloody nose. Or just apply to heavy bleeding.
Please note: This is not medical advice from a doctor. I'm a blog writer with no medical degree or naturalist experience. If you have an injury, see a real doctor. This is for use with fictional situations only. Thank you.