Whiteheads are lumps formed by oil trapped in the outlet. Blackheads are lumps of oil that push out from the outlet. They become dark upon exposure to air.  
Plugged outlets may become swollen and inflamed and then develop into pimples or sores full of pus. 
With acne, there are many pimples, whiteheads and blackheads. 
What to do: 
The best source of advice is a dermatologist.  However, there are some things you can do to minimize skin problems: 
    Do not be tempted to squeeze the occasional pimple because you may bruise the skin and cause infection. 
    Remove excessive oil frequently.  Wash the skin gently two, three, or more times a day, using a wash cloth, mild soap and warm water. 
    The dry the skin, pat it.  Avoid harsh pressure that could cause injury to the skin and spread infection. 
    Avoid stress or too much excitement as before exams or a part 
    Avoid some richer  foods and sweets, such as French fries, chocolate, nuts etc. for a few weeks to see if they are the cause.
     Avoid using face creams or lotions that contain fat or oil since they further clog the oil-gland outlets on the surface of the skin.