Can I get a tattoo nipple if I have scars and thin skin?

The short answer to this question is yes, you can get a tattoo.  That being said, the color of the tattoo doesn't always take well on a scar and may need a few touch-ups spaced over several weeks to months.  A nipple may not be reconstructed because of the thin skin, but a 3-D tattoo may be very helpful and can give you nice symmetry.  Overall, despite the failed attempt with the abdominal flap reconstruction, it looks like you ended up with a very nice result.  The addition of a nipple tattoo will make the result look even better.  Good luck!