Icon backpack rivet question - how to tighten?

[CrazyALee]

I must have OCD =( but I noticed a rivet is kinda loose on my icon backpack. I can hold the head side (outer round side), and wiggle it on the other side..somehow the original punch wasnt strong enough? Does anyone have any idea how the locking mechanism or punching works? Can I simply hammer the flat inner side to tighten it? Any help is appreciated thanks.