Hello, I'm 17 years old and have a small red bump on my penile shaft about mid-way up and on the left side. Its sensitive to pressure but not touch. It is no larger than a cm wide, also it's not attached it feels like it's just under the skin (It may just be a pimple?), but I've read some other questions that say their bump has turned purplish/ black and if possible I'd like to stop it before that stage by taking care of it now. Please help any advice is welcome.