|When you play your violin pay attention to your left hand position. Be careful that you are not letting the neck of the violin slide down to the point where it touches the webbed part of your hand between the thumb and the first finger. You should actually support your violin with your shoulder and chin, not with the webbing of your left hand. If your left hand is actually supporting the instrument you can't move your fingers nearly as freely as you need to!
Also, keep your hand position good. When you look up the fingerboard of the violin you should see a backwards letter "C" formed by your thumb and fingers.