I sold zinc mini march on 28th by mis but unable to buy

I sell the zinc mini on 28th march 2018 as intra day but on 6pm it shows me that commodity is matured. What is next happens, i will be charged more

Whenever you trade intra day, the position will be squared off the same day. If you want to hold onto the position for more than one day, choose NRML instead of MIS.