Saddle sores like you are describing are pretty common. It is probably your work chair...but any seated position with sufficient humidity can do it. It can be a perfectly comfortable chair and still give you sores.

What people have explained to me is that once you get a sore in a particular place, you are more likely to get a skin infection there. The more sores from the bike saddle, the more likely you are to get a bad pimple there because the skin is damaged and more prone to infection. Try staying dry. Use baby powder. Stretch your legs often at work, and try to air out in the bathroom a couple times a day. Antibiotic creams and vaseline also help, but the key is to stay very dry and very clean.