Yeah man, don't worry, I remember the first time that I pulled my foreskin back at the age of 14. I couldn't figure out what the hell that thing was, but I discovered it was normal after watching...porn
Yeah, who would've thought such a stupid thing could be somewhat educational? Anyways, if this is the first time you are pulling back the the foreskin, did you have a build up of smegma, the smelly white stuff? Also, when I pulled the foreskin back, part of it was still adhered to the coronal ridge of the head. Gave me a scare too, lol.
But relax man, you're fine.