Yeah just clean the copper free of paint, either scrape it off or use wire wool and paint it with some plumbers flux where the Hole is and then melt some Solder on to it and it should seal then then wash off any flux residue with damp cloths and re paint it If it had black paint on it in the first place if not then just wipe it off and leave it alone and then get a fridge mechanic to re Gas it for you,, All you need is a very small Gas powered torch and that should do the job like the ones used for soldering medium sized wires, but keep the flame away from all the plastic parts, Ok.
hope that helps.