Hello,
From the symptoms,it sounds like a boil or an infected hair follicle. Pls keep the area clean and apply some topical antiseptics. Also wear loose-fitting cotton clothing and use an antibacterial soap or mild soap like dove.Avoid any kind of cosmetics. Topical antibiotics such as mupirocin or neomycin containing ointment are also useful.In case the symptoms persist then oral antibiotics or incision and drainage may be needed.Pls consult a dermatologist in that case.
Also then the other possibilities of infected sebaceous cyst and swollen lymph node has to be explored.
I hope it helps.Take care and pls do keep me posted on how you are doing or if you have any additional doubts.Kind regards.
A folliculitis would respond to mupirocin application.If it is a node may need internal medication.