After having sex with my boyfriend, my inner left vaginal lip swelled up and turned purple/black and there's yellow crust? Around it? Rough sex cause?

Possible. You can have coital trauma and cause hematomas and bruising from sex. The yellow crust is a little less clear. Yellow crust and labial swelling could be from herpes, so it might be a good idea to see a gynecologist soon and if you're not using a condom, please do.