Also, if you don't pop a whitehead, will that leave a scar on your face once it's gone?

Possibly. First, if the scar is red or swollen, use an over-the-counter cortisone cream to calm the skin. You can also do laser therapy or filler therapy, within one to three sessions, laser skin resurfacing using fractionated laser technology can even out the skin surface and increase new collagen formation to help fill in acne scars. Wear plenty of sunscreen, sun makes the scars worse. Hope this helped :].
Scientific Rx. You'll usually scar either way unless it's small. The fact that you have to ask, and that you say you already have acne scars, tells me that you weren't treated as a teen as you should have been. You're 21 now and it's your privilege and responsibility to get clear. If topical benzoyl peroxide hasn't cleared you in two weeks, get with your personal physician for prescription-strength rx.