They key to treating pimples - to make them less noticeable, and ultimately go away completely - is to keep them clean.
Once a pimple has popped it is essentially an open pore, and as such is susceptible to become clogged up with dirt. So, as tempting as it might be, I would try to avoid covering it in concealer, and definitely try not to touch it as our hands carry huge amounts of bacteria and everyday dirt.
A simple but effective treatment is to dip cotton wool into some hot water (as hot as you can stand it... without burning yourself!) with some salt mixed in and apply it to the area in question. The heat will open the pore and the salt water will clean and sterilise the area.
Another treatment which some people swear by is to apply toothpaste to the area as the chemicals in the toothpaste help to dry it out. The only thing with this is that it can sting a little, and also make your skin go red, so I wouldn't advise doing it just before you leave the house!