It sounds like there is an infection at the area. You will probably need to see a doctor to get either oral or applied antibiotics, or if there is a lot of pus within, the doctor may even need to drain it out via a minor surgery.
From your description it sounds like a superficial bacterial infection and he needs to see a doctor to get antibiotic treatment.
That will depend on the depth of the burn. If it was a superficial burn and the skin just peeled off, there will be some post inflammatory pigmentation which can gradually go back to normal in a few months to years. If it is a deep burn with permanent scarring, then the skin is permanently damaged and will not go back to its previous appearance.
There could possibily be folliculitis or inflammation of the hair follicles, which commonly occurs at the groin due to the multiple hair follicles there. It is typically caused by skin bacteria causing inflammation of the hair root and can be treated with antiseptic washes, ointments or oral antibiotics. However without a physical examination, this will be difficult to determine exactly,, and if it persists, you should see a medical professional for a proper evaluation.
There are multiple causes of hair loss, the most common cause in adults is female/male pattern hair loss. This usually affects the top of the head and the temples(in men), and spares the hairs on the sides of the head.
Alopecia Areata is a common hair problem affecting children and adults. This is caused by the immune system attacking the hair follicles, resulting in the sudden appearance of round bald patches. Less commonly, facial or body hair may also be affected.
Telogen Effluvium is the most common cause of generalised hair loss in children and also occurs post pregnancy. It occurs due to an interruption of the normal hair growth due to an acute stressor to the body: Acute illness, surgery, medications etc.
Dark eye circles can be treated with a combination of treatments. They target different aspects of the causes of the dark eye rings – these include lightening creams, laser treatments or injectable dermal fillers.