Hi, hypopigmentation usually develops after a few weeks and, in the majority of cases, resolves after a few months . The exact mechanism that causes this type of lesion is unknown, but a previous report indicates that melanocytes are intact, so it has been theorized that steroids potentially impair some of the functions of these cells .More frequently in dark-skinned individuals and can present with a linear pattern due to possible lymphogenous or vascular spread of the corticosteroid. Also possibility of local infection with continuous discharge.Get examined for secretions culture and microscopy. If only hypopigmentation means it may recover soon, but in case of discharge and sinus formation means need to consult your surgeon he will examine and treat you accordingly. Hope I have answered your query. Let me know if I can assist you further.