At the very least you can go to the ER or any dental office and you need to get an antibiotic to make the infection go away. You will be charged pretty much the same for either visit - and if there IS an infection you need to have the antibiotics anyway first.
Believe me, without insurance there isnt much difference between the ER or going to the dentist just to tell them you have a messed up tooth. I had a bum back molar for YEARS. Ten years. I have never had a credit card and racked up so much debt on just this one tooth that I was literally sued from THREE different places one year when I finally had a good job. All medical crap relating to THAT dumb tooth. Finally, when I had insurance (which by the way was thru a company I worked for for FIVE years that did software for insurance companies even) by then I had to pay $400 bucks WITH my insurance at the time.
At the VERY least - until then, if you can, first get rid of the infection because no one can do anything about it - but also ask if they can do a "temporary filling" on it --- many places will not because they have the theory that fixing it is the best method (which they are right of course) - but I had a HUGE gap in my almost wisdom tooth - and for a few years, despite the fact that everyone said I needed a root canal or it should be yanked, I found a few dentists over the years that would at least seal it - now, the seal only lasts a few months as they will tell you - but at least it wont get more broken or infected until you can find a way to not get it more broken or infected. You have to call and ask. Someone WILL do it.
Also, you might try a dental school. They mostly just do like fillings and stuff, but its real cheap. Just like going to the hair school when I wanted my nails done - it might take longer, but its way cheaper and who are you to complain? At least for a temp filling... but you need to get your meds first. Not only because they may not mess with you - but you need to know that if you DONT take the meds on an infected tooth that even ANY novacaine or pain meds they give you will work if they yank it or wok on it. I learned that one the hard way. The infection fights the lidocane and novacaine and everything!!!! TAKE the antibiotics first. First and foremost - go get those. You can get them at the ER right now if you are in pain and have just a few bucks. TAKE THEM.