Say my character is level 5 and I have 12 constitution (+1 modifier) with 25 total hit Points. What happens if I have 5 points of damage (20 out of 25 total hit points) and then I take 1 point of constitution damage, bringing down to 11 with no modifier? Do I go to 20 out of 20 total hit points, or do I go to 15 out of 20 total hit points?
Similarly: if I have 20 out of 20 total hit points and 1 constitution damage, and the constitution damage heals do I recover to 20 or 25 out of 25 total hit points?