I suggest that you try the card in other phones or in a card reader connected to your PC. If the other phone or PC has problems with the card then it means memory card is faulty.
But if that memory card works ok on other phone or PC then problem is in your phone. You will need to take your phone to mobile's service center for repairing.
I will advise that you try the card in other phones or in a card reader connected to your PC. If the other phone or PC has problems with the card then it means memory card is faulty.