It will help, if your villager is not elderly then you can restore the health on the bar, take him and give him water, and then feed him, then make him enjoy the garden, do it again, i found that does help alot, and then put him on farming or medicine, he will heal b4 you know it, if you leave him on research or building then he will continue to get injuries and will die, make sure you put him somewhere else, and hell be ok.

if he is elderly, his health will never improve. sorry.