I have recently noticed slight whitening of the gum between two of my bottom teeth. it's sore to brush and looks slightly inflamed. i brush regularly?

Depends: It could be many things. Generally speaking if it doesn't get better in several days you should see your dentist. It could be as simple as trauma to a viral infection.

Paradigm shift: You're brushing, but you're not cleaning between your teeth where toothbrush can' treachery. Must floss or water-pik every day. Have area examined by your dentist, especially if inflammation doesn't resolve in just a felw days from flossing. Gum disease requires professional attention.