Welcome to the forum. It seems you shaved in an awkward direction that caused your skin get inflammation and pimples
. Your skin is allergic and sensitive, try using mild lotions. Since you have pimples filled with pus, stop wearing synthetic clothes, wear loose cotton clothes.
Take care of your hygiene and wash your pubic area at frequent intervals (after exercise or when you get any discomfort), keep it dry and use a mild medicated powder.
Ideally if you take care of your hygiene and sanitation the problem should go away in 3-4 days. If you do not get relief, get examined clinically and get all the blood tests done to rule out any major infection. Take care.