Hello,
Without examination,confirmation of a diagnosis is tough but it can be contact dermatitis,rash due to friction rub with clothes, dermatitis (atopic, contact, allergic) or excessive sweating causing sweat dermatitis.
You may try calamine lotion on the rash.You should also maintain hygiene and try to keep the area clean and dry, wear loose-fitting cotton clothing. Also use an antibacterial soap or mild soap like dove.Avoid any kind of cosmetics.You can also use a barrier cream with zinc oxide paste or calamine lotion or Neosporin cream on the bumps..
If the bumps persists then it will be best to get it evaluated from a dermatologist.
I hope that helps.Take care and pls do keep me posted on how you are doing or if you have any additional queries. Kind regards.
Folliculitis.Wash with antiseptic soap.Mupurocin application help.