I'm 16 and I have a small bump under the skin in my pinky finger and it doesn't move and is hard I've had it for a few months?

Wart? Without a picture to look at or being able to see it and feel it in person it is difficult to say exactly what this is. Commonly it could be a wart. Rarely could be something called a synovial cyst or tendon sheath cyst. Best to see your doctor for evaluation. Hope this was helpful. Best of luck. Dr. R.