Its called a frenulum. Its on the back side of the penis. We all have them. I am uncircumcised and have mine. Most circumcised guys still have them, although some might have had theirs removes with the snippage. It is normal dont worry about it. It being sore it not really something you can prevent. Maybe just try to grad it differently or put less stress on it.
That would NOT be a wise move. One of the capillaries leading blood to the glans runs just under the frenulum if I'm not mistaken. Cut into that and you'll be screaming like a pig all the wqay to the ER. We don't want that kind of injury, now do we?
sometimes i wish i could cut it off cos it slows my gains down cos it keeps wanting to try and tear after a few days of Penis Enlargement and i have to up to 2weeks for it to heal, also cos of the healing its become nobally.