I have a cyst on my back in the middle by my spine. How can I get it to go away? I have had it for a month but last night it was the size of a quarter,red and hurt

I'd start by visiting your doctor and see what they can do... there is no magical crème you can put on it and make it go away... but they might be able to remove or at lease aspirate it.

You need attention from someone else. If you don't have anyone who can spend time on it each day, you are going to have to go to a doctor or clinic. Cysts usually resolve themselves, but it depends on what's inside them (water, fat, hair, etc) and where they are. Being on the spine is probably irritating it each time you move. If red and painful, it could also be infected. Better go to a clinic.

It's near my bra line. Could it be acne?

Most likely not acne. As noted, has someone been helping treat it for you

Acne the size of a quarter flattens out at the edges, while a cyst is a bit of a dome, even if a very low dome. They are easy enough to tell apart. It does no good to ask people 'could it be.'