Hello and thanks for the query
I think it is a bacterial infection which might have occurred due to boil or any other source. You need to take a course of oral antibiotic along with analgesic
and anti-inflammatory drugs. Antibacterial ointment or cream ca be applied at the site.
Keep the area clean and do not try to squeeze it. Let it heal by its own. Consult your GP so that he/she examine it and get to a diagnosis. You have to treat it as it is painful and swollen.