it looks perfectly cool to me! aren't hedgehogs kind of derpy animals anyway?

Whoever said that is a jackass. They know nothing about tattoos and even less about being a decent person. I'd leave the tattoo as is. I say this over and over, I think you have a better chance of making it worse than you have improving it. It's a nice tattoo. Did you see examples of the artist work that looked like what you wanted? 

Your tattoo looks just fine! You are also comparing it to work by Wendy and Tomo which are incredibly high standards. Me, I wouldn't touch it but plan to add more to your leg. Good luck!