I had one.
It sucked massively.
The doctor will always try a antibiotic first in case it's just a boil/regular cyst. But if it's a large bump on the end of the tailbone, and it looks sort of like a bubble surrounded by crust, and disgusting ooze comes out of it... it is probably a pilonidal cyst.
Chances are the medicine will not work. It'll only shrink the cyst into a small dimple that doesn't hurt. Don't be fooled, go to the doctor to have it checked. Because if you don't, it will come back, bigger and badder than before.
Lancing will relieve it temporarily, but the only way to really get rid of it, for most people, is surgery. The bigger it is, the bigger chunk of your ass will be carved out. So trust me, get rid of it as soon as you can. If you put it off for money reasons you'll regret it.
I had to have two surgeries to get rid of mine. The first got rid of the main base, but a offshoot remained, and developed over a year. I went back to get rid of that one. I'm pilonidal cyst-free for 3 years now *knocks on wood*.
I'm going to have my ass lasered to get rid of all that damn hair. That will decrease immensely the chances of it coming back.
Sorry for the gritty details, but I thought you should know. It ain't no laughing matter.