if you press cntrl+t you will open your character screen, in the lower parts you will see a button called injuries, if you press it you can see what injuries you have, wich is what lowers your hitpoint.
if you wait, even when offline, a lot of them will heal, if you see one that doesn't say it will heal itself, you can browse here to see what you need to fix it
http://ringofbrodgar.com/w/index.php?ti ... edirect=noalso if you can find a giant fallen tree (that appears on your minimap) you might get some acient roots, that will randomly heal some of your wounds