What Causes Stiffness In Finger Post Sutures At The Finger Base?

I have ten stitches on my middle knuckle at the base of my finger. I had a a fairly deep cut that was down to the tendon. After four days it is still very swollen and red. My consern is that I can not move it like I should he able to. I can not straighten my finger, not from pain there is no pain it just will not go.