do work son

Big Black (best known for his role on MTV's Rob & Big) is credited with this saying -- in fact he has a clothing line named after it (dowork.com).

Do work means to do your best, get after it, step up and push through barriers, overcome & achieve, etc. It's basically a way of encouraging someone to work hard. A more redneck version would be Get'er done!

Son in this usage is referring to a close friend or at least someone who would appreciate the colloquial/familiar greeting.

Person 1: Man, I need to get some good grades this last semester...
Person 2: Do work son!

Person 1: Just landed an interview with this great company and hope to make an impression.
Person 2: Do work son.

Person 1: Imma get swole as fuck!
Person 2: Do work son!