If you are close with them, and they mean something to you, why not try and make things right? Even if they both are only friends, that doesnt mean you cannot have a strong relationship, im sure they arent feeling to thrilled about what happened either but there are always disputes between people, its a part of life. Dont let something like this ruin your friendship, you have realized that you've done was wrong so go fix things :)
All you can do is try ^_^
If they're best friends then just fix it. What makes people a true friend is the fact you can argue with them and always find a way to make up. If they're just half as important as you say they are I can assure you things will work out with good talk.
All you can do is try ^_^