external sd - Why is my microSD card not being reconized in Samsung Galaxy S Plus?

I had purchased Samsung Galaxy S Plus, it was working fine, but I had a problem yesterday connecting it to my PC. After that my SDCard is not being recognized by my device. It says Your phone doesn't have sdcard inserted also when I try to open the inbuilt camera its also not working with a message as Turn off USB storage before using camera. I tried to check that my SDCard is not corrupted so testing in other devices and its working fine. I also tried to restart the device couple of times. So, can anyone suggest me what can be the problem here? why my SDCard and Internal Storage is not being detected?