You can try vitamin E creams but they are not always real effective in reducing scar tissue and take a long time when they do work.
Read information here and on the net about Peyronie’s disease, which is basically the same issue only on the shaft of the penis rather than in the frenulum area. Most docs are suggesting one or another of various surgeries for Peyronie’s. Several of these result in shaft shortening; in your case, some cosmetic work on your frenulum wouldn’t cause shortening. But get someone good, if you do this, because the frenulum is a wonderful and exquisitely sensitive area.
If your brand of scar tissue doesn’t interfere in any way with your sex life, ignore it is my advice.