In my novel, I'm currently writing from a male's perspective and I need a bit of help. It's not an erotic book, but I'm writing a flashback from his teenage years which involves a bosom hug and I think it's realistic and fitting to mention something subtle about him getting excitedan erection but I have absolutely no idea how to phrase it.
My character is a very reserved individual, who would never use your typical terminology. In a previous chapter, he referred to masturbation cryptically as a "catharsis" (which was fitting in the context).