What drug-store brand concealers work well on acne?
Specifically, I have a very large, raised, red bump right in the middle of my forehead. It looks like I'm trying to grow a unicorn horn.

I very seldom get acne, and when I do it's usually one or two small white heads that I pop (I know, I'm terrible) and by the next day my skin looks good as new. But yesterday I woke up with a raised bump on my forehead about the size of a quarter. It's really tender and red. I hoped it would go away by today, but no luck.
DF's mom's retirement party is tonight, so I'd REALLY like to get something to at least take some of the redness and shininess out of it. Any suggestions? There's a Target and a Walgreens within walking distance of my office.