I know EXACTLY what you are going though. The feeling is normal, its part of the arousal process, you prob mentaly blocked it out due to your trauma.
Quiting smoking will help, smoking causes a range of health issues inclusing effects on libido and erictile problems.
if you wish to talk about your issues with someone who went though the same thing, let me know. I use yahoo im.
I believe you are talking about mild tingling senstion in the penis, glans and groin area duing the state of arousal and erection. It is a normal sensation during sexual arousal.
Smoking is a risk factor for development of erectile dysfuction therefore your decision to stop smoking a good move.
AT