Flaws in a character are what make them human and relatable to a reader. I've discussed making characters flawed before, but those were flaws in personality. The type of traits that might make a character annoying or unlikable but may be redeemed by other traits.
But now it's time to consider flaws that the character doesn't like. Does your hero want bigger fore-arms? What about the ability to hold a meaningful relationship? Does your heroine want to spend more time with her family but can't because of her career? Or does she wish she'd spent more time on her education? Maybe she wishes she didn't care so much about her appearance but would prefer to spend more effort on the people she cares most about.
And don't be afraid to look to your own life for examples. It doesn't have to be something big. It could be something simple and stupid. I, for example, STILL wish I could grow a beard. Sure, there may be other things that I would change if I could, but as far as character and personality go, I am putting effort into those. The one thing I CAN'T change but REALLY wish I could is that STUPID BEARD!
The protagonist in my current book wishes she had a prettier laugh. But instead she snorts. Loudly. And it bothers her.
So take that for what it is. But make sure you have an unchangeable flaw for your characters so they're relatable to your readers.