ive been playing for four years and im the rhythm guitarist of my band (Metal) and i am known in the area to have some of the chunkiest palm muting etc, point is im good at what i do (im not being cocky just confident)...but as of late when i palm mute the bottom of my thumb on my right hand starts to hurt and it has me worried cause its never happened and i was wondering if its A. a muscle that needs to be checked by a doctor or B. i havent played too many songs with alot of palm muting like i used to to my muscle is just building up.

help/advice would be appreciated alot...thanks.
My band is Ancient of Days (A.O.D)...we're a decent band hailing from the most Un-metal place in the world, Miami Florida...check us out at www.myspace.com/ancientofdays

Metal Will Live Forever!
Probably B

If it still happens after a few more days then check for A