Hello, Doctor. I Seem To Have Recurring Small, Pus-filled Spots

Hello, Doctor. I seem to have recurring small, pus-filled spots appearing on My left jaw gum line. I Had a spot appear a few months ago. I managed to pop the spot which released a small amount of pus. I rinsed and cleaned My mouth and teeth. And I've now had the same little problem occur again. You should know that the tooth where the spot appears, once had an infected abscess in it. My dentist removed the abscess and cleaned the cavity in the tooth, but didn't offer to seal the cavity. I have no pain, as the nerves were removed. But why am I getting spots in My mouth, on the gum line? Thank you so much for any advice and help.