Disassemble the offending bolt, and examine the tip of the firing pin under magnification. If it has pierced multiple primers, it's probably been damaged by leaking gas. The tip probably has a burred or rough area on it now, which will only make the problem worse. If it is damaged you may be able to repair it, but the smart money is on replacing it. Also examine your bolt face and firing pin hole under magnification. If the firing pin hole looks wallowed out in one area, it's may also need repair.
I would contact the maker of the AR and tell them. I got a new firing pin for an AR I had a few years ago. Slightly different problem as mine didn't make the cartridge go boom. They sent me a free firing pin which fixed the problem.
I would echo the other guy above that said you can't tell by looking at the firing pin if its out of spec. Its thousandths of an inch. You can't see that with the naked eye.