OK. One more time. Bones, be sure and cut and paste your standard answer here, too...
This is NOT natural. Not natural at all. There may be something wrong with the pitch and/or span of your bowling ball, or there may not be. But get it checked anyway.
Numbness should NEVER BE IGNORED. Did I yell loud enough? NUMB MEANS NERVES ARE INJURED. It could be that these nerves can be damaged FOREVER.
Get to the doctor. NOW. Get your hand, wrist, elbow, arm, shoulder, and neck looked at. If you want, I'd recommend a chiropractor as well - they can fix some stuff like this much quicker than a standard MD.
Regardless - get it looked at!!!!!!
I've been fighting nerve and tendon damage in my right arm for 8 years, and in my left for 6. It was caused by a systemic problem, and is finally getting better, after weeks and weeks of physical therapy. Turns out mine is not caused by bowling, but by work (hours and hours and hours on a computer with a really bad workstation).
But you don't want to hit your later years unable to keep up with the kids just because you were stubborn now....
Like me.