2 days ago i popped a small pimple on my face. now it's dark red, very hard, warm, and the size of a dime. it is raised and doesn't have a head.

It could now be: infected. put some antibiotic ointment on it, and see doctor if not better over next 24 hours.

Probably Infected: Its easy to introduce bacteria into the area when you pop a pimple, and this sounds like it is a small skin infection setting up, especially the warmth. Try some neosporin creme on it tonight and see how it looks in the morning. You may need an oral antibiotic if it worsens overnight. Good luck!

Infection: Sounds like a skin infection or abscess. You could try warm compresses, but if it persists or worsens, you need to see a physician.

Popped pimple: Its possible that the pimple is now infected and has become a small abscess or cellulitis. Use warm compresses and bacitracin or neosporin and have a doc look at it asap.

Did it drain?: Did you manage to expell the sebum/pus? You may need to squeeze out more. Bacitracin and neosporin and triple antibiotic are all completely useless. All 3 are among the most common things that people are allergic to. When it is fully drained it will heal better. Sometimes it helps to inject a cortisone into inflamed acne. A dermatologist will help you if it fails to heal promptly.