3 Year Old Son Won't Stop Picking Fingers

Sighhhh . . . . . imnsho, this behavior is a symptom of something else.
Seems to me he wouldn't need to do this if whatever the underlying problem is were determined and dealt with.

You're in a major metropolitan area.
See if your local university has a program where
psychology students or therapists-in-training
have office hours to work with clients.
The therapists are closely supervised by faculty members.
See if there are opportunities to work with play therapy trainees.

hello
I believe in part this to be inherent . My biological family has many nail biters in it. Additionally, as a young person (and even now when nervous) I pick at my fingers. I have read articles where nail picking/biting can be equated to the same type of anxiety as those who pull out their hair (Trichotillomania) sounds strange doesn't it, but true.. Also, some might say.. ah stop picking at your nails, you can do it.. true.. you can.. but when it's something you've done from such a young age, it becomes very difficult to stop. My mom used to get so upset with me when I would start in, but I often did it without realizing I was doing it. Not to mention, I truly believe it was a built in mechanism for me that I used to fight anxiety or stress.. Now, as an adult, I can manage better, however I will say, stress can still bring on a bout of picking at my fingers as can different foods such as too much caffeine or even sugar. I try to limit both.
Exercising has also helped me to not pick as much.

Could be anxiety related. I would talk to his doctor. As Shira said, there could be something more underlying this behavior and you don't want him to progress in self-harming behavior. Good luck.

Well, he definitely likes to pick, doesn't he? Some kids pick there nose, some their fingers, some are nail biters. It's a habit that's hard to break because the source is always there. Have you asked the pediatrician for some suggestions? My son would chew his fingernails until they were so low they would get infected. He would do it during story time in kindergarten. He's 17 and I still have to get on him about it.