What Causes Itchy Lump On Penis?

What is this large lump on my penis? It is really big and i didnt notice it half way in the day when i went to the bathroom at school. As soon as i noticed it it began to itch especially as i walked home. I cant squeeze it, nothing comes out. The itching has stopped. It doesnt hurt when i touch it only when i squeeze it. I think it is a cyst or something but i am not sure. What is it , how do you think i got it and how can i remove it? Will it go away ? Is it dangerous ?