I got all four of my wisdom teeth pulled 4 year's ago and a couple days ago a bump appeared on a socket and it's kind of sensitive, what is it?

See dentist: It will take a dental exam with X-ray to find out what is causing this bump and the best treatment. Schedule an appointment ASAP.

See your dentist: you need to find out why there is a bump and where it is coming from. It can be a growth or an abscess from either the tooth in front of it or a gum or periodontal problem from that tooth. So please see your dentist to have it properly evaluated

Sequestra: also called bone fragment or tooth splinter as a complication of wisdom tooth extraction. See your surgeon for examination, x-ray and treatment.