Uninstalled macOS Sierra installer but corresponding disk space(~4.88GB) not freed
The problem is with a disk image with the name Apple RID... created by the macOS Sierra installer which did not get ejected when macOS installer was deleted and was occupying around 5.5GBs and wasn't visible anywhere except in Disk Utility.

After ejecting that disk using Disk Utility and restarting the laptop, the memory which was held up got freed.