What Causes Small Bump On The Penis?

i am shy about this but about 2months ago, i found a little bump on my penis and it has a white head. its not a spot before you think it but it looks like a wart and i cant pop it and im afraid of it. i have only had unprotected sex with my girlfriend of 1 and a half years and we both havent cheated. im afraid the worst can be that i have given her a genital wart but i dont know how i got it or she got it. if it is, then i couldnt live with knowing that she has one. please tell me some good news, or a soluton. i need help and im scared of your answer.:(