In a comment, you write:
I’ve been here for almost a year already and planning to stay until I get my PR visa.
Since your residence is temporary only in terms of the name of your legal status, you should apply for your new visa in South Africa. Here's what the US State Department has to say about it:
You should schedule an appointment for your visa interview at the U.S. Embassy or Consulate in the country where you live. You may schedule your interview at another U.S. Embassy or Consulate, but be aware that it may be more difficult to qualify for a visa outside of the country where you live.
You live in South Africa, so you should apply in South Africa.