What more thoughts than “it’s a common reaction”, can we give? Apparently, you couldn’t resist it, could you? She broke that barrier by merely her presence, which makes your “indriyas” not so strong after all.
And, yes, I’ve had similar experience and tons more of other events going on after a Lilith evocation. That ended with a double marriage with a succubus and herself. You poked Lilith’s shoulder and got a boner. It’s normal. 
Well if you would know what indriyas are you would also understand to observe without doing anything about it lies the strenght, ordinary fleshbags would been overwhelmed by the experience and fapped their dicks of, I noticed that sum outward force effected my bodily functions, I observed and found it fascinatiing. I can understand that you dont know what indriyas is and therefor see weakness by a bodily function, missing the point all together. Even Kali havent had the luxury to break my self-control, nor will Lilith; and she apparently when I was a child tried to scare the shit out of me and that didnt work either, my tantrika initatory name is Govinda - he who controls his indriyas. My tantrika guru wouldnt given me that name if he did know that I would act on a simple thing like an erection. Kinda ignorant so please keep your projections to yourself brother. <3
Yet, the result was an erection, despite your claim of mastering “control” over it. Where is the “ignorance” in my observational statement? The Lust Current is all about losing control and few magicians, if any, can’t physically resist it. You better learn how external energies work, before throwing ignorance, so keep your own projections to yourself.
You still miss the point (twice), and apparently you can’t read either what I’m writing or read between the lines I’m writing and still project your ignorance. You are wasting my time so this discussion with you is now over.
In my experience with calling upon Lilith, she brings great sexual energy with her, so you are probably feeling the residual effects of the ritual on your body(especially if you didn’t banish all her energies. Also, it could be that a child of hers(succubus) is visiting you and causing your arousal to “play.” 
Also, about West and South: the first is related to the Moon, and the second may add the “black” element (Lilith, the Black Moon)… so two particular possibilities are west alone or southwest.
Face the West, burn some incense, lite a red candle, prepare some present, jewelry is fine, a chalice of red wine, prepare personal invocation, blood letting is the best offering, anoint her sigil with your blood and start meditating. Do it for at least three nights in a row. Put down your experiences and dreams. She has a wild nature, so be honest in your approach. You can also expect that she will come and go whenever she wants, anytime after. Once you make a connection with her, it will last forever. Never try to control her, just an honest approach.
Good luck!
Tip: Be clear with what you want!
And one thing at a time!
That is where i messed up XD
North. Since its a dark spirt. But its up to u