Don't worry. You have the right to have fun just like anyone else.
I'm quite the fan of DC and Marvel, and both have some really amazing black characters! It's something to consider if you're into superheroes, there are plenty of positive, really interesting characters.
Depending on how new you are to cosplay, some characters you like might be beyond your skill level, but that happens to everyone. And like what Falclon said, you do have the option of working with characters outside of your ethnicity if need be - sad but true, a lot of popular media that cosplayers work from tend to be a little monocultural sometimes, so it can be limiting. But don't lose sleep over it! There's so much you can do and so much you can learn.
Sorry for sounding like a corny Hallmark card there though. But seriously, go forth! Enjoy yourself!