A couple years back, I developed an issue where underneath my thumb nail gets dark, and very tender.  This seems to happen after 1/2 a game or so...  By the end of a 3 game league, it hurts to touch.  I haven't intentionally changed anything in my grip (or release).... 

My current span is 4 5/16 by 4 7/16 and is relaxed.  Thumb is 1/8 rev and 1/16 right (palm). 

I did (intentionally) drill an oval thumb at the end of last year, but saw no change...

Has anyone seen this before?  Any ideas/suggestions?

Thanks,

Scott

Either your span is too short or you have too much reverse pitch.
Take a look at this:http://wiki.bowlingchat.net/wiki/index.php?title=Jayhawk_Fitting_Tips
When was the last time you had your grip checked?
You can check that here:http://wiki.bowlingchat.net/wiki/index.php?title=File:MorichFitting.pdf
You don't need a fitting ball. I just use a current ball.

Effen 10, I would think that would be too much forward pitch.

From looking at the nail that means that the thumb is rubbing against the slug and breaking blood vessels. Does the same happen to your fingers? The thumb seems to be too relaxed causing you to grab because the thumb wants to exit earlier, especially if your span is also relaxed. Also, your thumb may be to big or the oval could be in the wrong position causing the thumb to rub. A relaxed span is designed to get you to relax you hand and come out of the ball with little to no grip pressure. With that said you dont need a relaxed thumb and span. Finger pitches can also have a big influence on the thumb. If your finger pitches are reversed as well, that could cause you to grab. What are the finger pitches?

I had taken about a year off afer school,then got back into bowling.. around that time, I started to notice it.  At the time, I had my span checked by a few different people both local and at the nationals booths.  No major changes.. little tweaks...  still had thumb problem.

I do have a little reverse (away) in my fingers as well, due to less than average flexibility.
 
maybe span is the issue and needs to be lengthened a little...  hmm

I appreciate all of the posts/input!

You rub the back of your thumb due to the way it exits. If it is being delayed and you are over rotating at the bottom, it will rub the back of your thumb. IF the span is correct I would consider going more away with the lateral, try an 1/8" left to see if that relieves it.
Remember when you injure something such as that it will not automatically go away, it takes time for the pain to go away.

It is truly Nasty looking!  Something is off by a good amount!

Like the above posters It's very possibly too short a span.

Regards,

Luckylefty