Compulsively flip the knife open and closed for a few days and everything will be fine. Your thumb will eventually get used to it. I went through the same thing when I first got my Ricochet, felt like the darn thumbstud had taken all the skin off my thumb, and it got to the point where I couldn't even open it anymore. Of course I cycled the knife about a thousand times in well under a week (speedsafe is addictive) which is kinda excessive, but it really helped with my technique and after my thumb stopped being numb I could open it without any discomfort. I think the key is to push more forwards than out, play with the knife a lot and you'll find what works best.
