It's an abscess, take the antibiotics before it blows up on you. If it comes back you will probably lose the tooth. Rinsing your mouth with 50/50, 2% hydrogen peroxide once in awhile can prevent gum problems. Not every day, it kills all bacteria, good and bad, can cause thrush. Once a week to 10 days should do it. Let it soak on your teeth for 30 seconds to a minute and rinse. It can burn your mouth if you don't rinse.
I'm not a Dentist, just a crown and bridge technician. You should consult with your Dentist before you lose that tooth.