"Dent" on side of penis?

  For many months now I have had a "dent" on the side of my penis when it's erect. It suddenly appeared last year. I don't recall any particular events or injuries before I noticed the dent. It is not painful and doesn't cause me any problems. It doesn't affect the appearance of my penis overall, it's just a very obvious dent on the side.
  When flaccid, I can feel a slight difference in the density of tissue near the dent (it's a little more dense there), but there is nothing hard, no lumps, nothing seems wrong.
  There has been no noticeable change in this dent as long as I've had it.
  Is it something to worry about? Did I "break" something during sex? What's going on?
  I'm 31, white, married, in good health except for a mild case of psoriatic arthritis. There is no risk of any STDs from extra-marital relations. My wife has had a number of yeast infections in the last few years (none lately).
  Thanks for your replies.
======================================================
Dear DM,
Peyronie's plaque is scarring of a layer of tissue (tunica albuginea) which covers the "spongy" erectile tissue in the penis.  There is evidence that the precipitating event in Peyronie's disease is trauma.  
Trauma often takes the form of sexual intercourse which is often frequent and vigorous.  Certain sexual positions, i.e. the woman on top, have a stronger predilection for plaque formation.  It is the plaque which is causing the bending/curvature in the penis.  
How the plaque presents may vary.  Some people notice pain/painful lump in the penis, then a small curvature of the penis which may progress.  Others notice the curvature appears almost overnight and does not improve or worsen from that point.
If the curvature of your penis doesn't interfere with your sexual activity, no medical/surgical therapy is warranted.  You may search the archives of previously answered questions regarding Peyronie