Lump under skin on penile shaft

I'm 15 and a virgin.  Yesterday I masturbated then a few hours later I noticed a very mild pain, almost just an uncomfortable felling on the left side of my penis. When i looked it almost looked like a raised vein. When i pushed on it, it was hard under the skin. It felt like it was a hard vein. When it is erect you can see that it stretches across the penile shaft.  It has been itchy and is continueing to be uncomfortable. It doesn't hurt when i masturbate or touch it.  But when i am just sitting there i feel that uncomforable pain that i was talking about.  I told my dad about it and we decided to just leave it to see if it goes away but if it continues to say, or get worse we will go to the doctors. I just wanted to get an idea of what it could be. It isn't red, it just is a skin colored lump. It isn't attached to the skin either. Please reply quickly! thanks you