Sorry to hear that you have nose bleeds. In my 14 years on this forum, I've never heard anyone with nosebleeds.
Congratulations on getting to day 21.
Are you taking anything else besides water?
Drink warm water as per thirst, rest plenty and keep warm. If you bleed again sit down, kneel forward and put pressure for 5 minutes on the nostril that is bleeding, I think it is your left side. If it does not stop try again. Other things you can do is to rub ice on the side of the nose that is bleeding.
Lie down after a bleed and let the blood pressure go down a bit.
This will pass.
Keep us posted. You achieved a lot, don't let it go you are still cleaning.