@Abhinov-Singh-0 A permission denied error means that some or all of the files in that directory are owned by a user that is not the same user as you are logged in as.
It also suggests that the images may have restrictive privileges that do not allow them to be read by the user running the NodeBB process.
Try this:
cd /path/to/nodebb sudo chown -r $USER public/uploadsThen try to run NodeBB again.