Tooth extracted 12/3 just noticed knot on gums, slight pain not bad infection or normal?

Sounds normal: As i said this doesn't sound like a problem but is this getting better or worse...If its getting worse then see your dentist if better its still healing.

Probably normal: It is possible to get a collection of blood, a hematoma, after surgery. This will typically self resolve and improve each day and week. If not, have your dentist or oral surgeon evalaluate for infection.