My car tyre punctured

Last weekend, my car tyre was punctured by this single big nail. Lucky me as there is one tyres shop which opens on Sunday. My car tyres had not been changed since 2004, so i ask the repairman to change it to a new set of tyres instead.
So after taking out the old tyre, this is what i saw

A TUMOUR?

To my horror, i SAW A TUMOUR GROWING OUT OF THE INNER LAYER OF MY TYRES!! But after closer inspection, it was some sort of rubber used to fill up the hole of the punctured tyre. This is not the first time i punctured it. 

BUT (second but), how come there is another nail there? 

Then i come out with few theories.

1) I got hit by two nails at the same time.

2) The nail wasn't taken out during the last repair. 

a) The previous repairman hates me and purposely left the nail inside.

 b) The repairman pull out the nail but half of it broken and left inside.  

What if the nail went inside my tyre? Will it explode? Would it be like putting a needle inside a balloon? Anyway, luckily i found out earlier. I will insist the repairman take off the whole thing next time.