Thank you for your query at DoctorSpring.com
There are medications like antiandrogens, LHRH agonists and antagonists that can shrink your penis as well as do away with erection.
The side effects do exist for all these medications but are very minimal.
Feel free to discuss further,
Patient replied :
I should have include my reason for asking. My wife of 20 plus years has a tilted uterus and two years ago she injured her back. This has limited our sex life and required I keep myself in a position that does allow for full penetration. This also makes it difficult for us both to relax at times. If my penis was simply one inch less in length we would be able to relax and connect better. So, I still want to have erections but it would be helpful to loose an inch. They make rings and other things that can go around that base but it would be better for us both this way. I know this is an unlikely and rare request. But I thought it was worth a shot.
I am sorry there are no such methods which can shrink your penis.
Medicines will affect your erection and can lead to impotence.
Unfortunately, I do not see a way out in your case.