Skin growth on arm

I had an itchy pimple like spot on my arm that was not raised, but I squeezed it a couple times and some dry white stuff which looked like dead skin came out.
After I squeezed it recently, I noticed that there was a growth inside my skin where it had come out.. sort of like a small sac. Well, I picked at it and it came out. It was a small white sack looking thing that left a small hole in my arm. Now I'm scared that I may have done some damage.. can it cause cancer?
I'm really nervous right now.