My face is now bruising 4 days after wisdom tooth extraction. Why? What can I do about it?

I had my wisdom teeth out on Tuesday. The swelling reached its peak on Wednesday, and then gradually got better. For the first three days (too long, I know), I was using an ice pack on my cheeks to make the swelling go down. Today (Friday), I realized I should be using heat, so while I was memorizing some stuff for school, I laid on my bed with my cheek on a heating pad. It felt good! When I came upstairs to do some other school, my mom noticed my jaw looked bruised. Just a little bit yellow, but still odd.

I have to work this afternoon, and when I get off, I’m taking a friend to supper. I don’t want to look like I got (symmetrically) slugged in the jaw!

Why is it doing this? Was it a reaction to the heat?
Will it go away? What can I do to get it to go away faster?
Can I still use heat? It felt really good, and I think the swelling went down, even though the bruising started.

Thanks for your answers :)