Suggest Remedy For Swelling In The Index Finger

my index finger on left hand by the knuckle in the middle is swollen and hurts when touched.. it is swollen all the way to the top of the knuckle towards the hand. I did not injure it in anyway it just popped up one day and it is going on day five. i tried an ice pack and a finger splint swelling is not going down and still hurts