Apparently fibrous tissue build up is not a common problem, as no one here seems to have any direct experience with it. I was just trying to look at all of the possible problems I might encounter.
I did an internet search and found that there can be a problem with fibrous tissue build up in the corpera cavernosa (spongy tissue) inside the penis that retains the blood that controls erections.
This appears when the same injection site is overused. It can cause even more problems with erection. Oh well, one thing at a time.