I had a white round bubble on my gums where my wisdom tooth was removed (over a year ago) i made the mistake of poking it with a needle, how can i prevent infection or know if it is infected? what would a small perfectly round white bubble be?

Probably a blister. Use Listerine or another mouth wash and if not better -your dentist

Many dozens of reasons for "white round bubble." Poking it with a non-sterile object not wise. You cannot diagnose this yourself, which means you cannot pick appropriate treatment. Pleasehgave lesion evaluated by your Dentist or by a specialist ni Orsl Surgery, Periodontics, Oral Medicine, or Oral Pathology. Your problem cannot be diagnosed with just a computer click.