Is it normal for childhood trauma to affect my obsession?

I have an obsession for smelling my penis especially when i haven't washed it. I spoke about this briefly on a previous question and mentioned having a childhood trauma i think may have caused it.

Basically the event I think may have caused this was one sunny afternoon when i was about 14 or 15 sitting up in my room masturbating. My grandad was downstairs at the time (he had been invited over as part of a family get together). As i enjoying my private time the door busted open...
I was shocked and terrified...
My grandad "Ranbin" with a furious look in his eyes put one finger to his lips and whispered "shhhhh"
I said quitely and hesitantly "grandad its not what it looks like, i was only itching it"
My grandad sneaked over and sat beside my on my bed.
"show us it then" he whispered softly in my ear.
"but grandad? i dont want to"
"get it out boy, i know how to fix it if its itchy"
I played along with my own lie, I didnt want him knowing i was actually masturbating. I took it out and showed him and said "grandad its just like really itchy near the tip"
"ill see if it smells funny"
He bowed his head with a mr bean smile on his face and sniffed the tip. I remember his eyes going white.
"boy now thats no stinky penis. It smells like boring cheddar!"
He had seen passed my itchy lie. I was worried and scared.
"cmon boy I will show you how a real man smells"
My grandad whipped out his penis which flapped around like a wet savaloy and thrusted his hip making his erect penis fall directly under my nose.
"now thats a smell you wont forget" he said as tears ran down my eyes.

I dont remember if those tears were tears of disgust...
or wether they were tears of pure extacy...

I always have remembered that day.

Maybe i smell my penis to remember that day.
That one beautiful moment.
Lost in time.