Hi thanks for writing here.It seems you have developed contact dermatitis
due to garlic .Such things should never be tried specially where skin is thin like on face and genitals.You can just start applying a topical steroid
antibiotic combination like flutibact cream for one to two weeks which will help you clearing the dark patch.Do not apply anything on it,take sun protection.As far as your eybrow hairs are concerned if they are not growing then it may be alopecia areata
,in that case you can consult a dermatologist
and take further treatment for it.