My gum between my back two molars hurts really badly when I floss (which I do often), and there's a small abscess beside it... is there anything I can do to soothe the pain?

I don’t know if its a cavity (I’ve never had one before), and I always floss and brush… and we don’t really have the money to go to the dentist for a checkup right now, and I just need to know if there’s something I can do for the pain.

When I floss back there, all I get is blood and it really hurts to put any sort of pressure on it. Any ideas on what it is, or how I can help the pain for a little while?

Edit: I don’t have my wisdom teeth anymore.