No problem. I use a large hammer as a backup on the back side, then use the ball end of a medium size ball peen hammer to peen the ends of the pins.

Additionally, you should feel of the side plate by rubbing your finger over it. One side you will feel the burrs, the other side will feel smooth. Peen the pins against the smooth side. There will be more area and the slightly radiused edge of the hole will accept the peened pin better.

Good luck,