Unfortunately I have awarded a bounty to the wrong answer while I wanted to award it to another answer. Can I take back my points to award someone else's answer?
No, this is not possible.
You can start a new bounty and award it to the correct answer.
It may be possible for a dev to do this for you - if so, I am sure they can post here and confirm if possible.
No, once the bounty is set, there is no way to retrieve the points back, cancel or change the bounty. It says so when you are trying to start a bounty too.
In your case you could try to contact the support, or just live with it.