Hi I Have A Problem With My Right Index Finger,

Hi I have a problem with my right index finger, at the last knuckle towards the left side of the finger I have some pain an there is something moving under the skin. it slides from below the knuckle to above the knuckle on the left side. I can not put pressure on the finger while tryin to pick up something or just using the finger. I don't think it is broken, but then again.. what could have happened ?