You are unable to stand up, and therefore unable to cut down trees or bushes to make kindling to fix your leg. Even with an axe equipped looking at a bush with the option CHOP KINDLING, your character will forage for berries rather chop down the bush. This may be intentional, but it seems unusual to stop you gathering to fix your broken leg.
Also in the build i played recently on experimental, the ability to search the ground for sticks had been removed. This would be a reasonable alternative if reintroduced.