Tips on how to stop?

19F! I’ve been picking at my thumbs for years. I think I’ve been doing it since 2nd/3rd grade. I want to stop because I just feel embarrassed when looking at my thumbs. I’ve tried many times before but I was never successful. The most amount of time I’ve left it alone was about a month before I started again. Also, is there a way I can make sure they heal correctly? Will my thumbs end up looking off?