Best method: get a small machine screw, a nut and two washers. Small enough that the follower can't snag on the hole, 1/8" or 3/16". More threads per inch is better, because this is going to be a lot of torque for a screw that size. The washers need to be bigger than the dents so you can only see undamaged metal around the top one. Drill a hole in the dent for your screw, slightly bigger than the screw (the stretched metal is going to need somewhere to go when you press it back into shape.) Grind/sand two sides of one of your washers until it fits in the slot the follower rides in (where the dent is.) You may need to make a few of these if your screw head hits the slot before it contacts the washer. If your washer already fits then great, skip that step (you may still need a stack though. Pull the follower and spring and insert the screw with the ground on washer(s). If your screw is a hexcap and short enough to fit down the magazine body narrow-ways, save yourself some frustration and put it in with a pair of pliers from the inside with the hole facing down (don't forget the washer(s), and you can hold the screw by the threads just below the washer(s) if you're having trouble getting it down the slot.) Then apply the regular washer and nut to the other side, finger tighten and put a wrench on both of them. Turn the outside wrench until you're pretty sure you're about to strip the screw (no biggie if you do, just get extra) and you should have a flattened out dent with a hole that isn't likely to make the follower snag and tilt.
Less good but easier way: drill the dent out completely. Place a washer or any other flat circular object which can fit through the hole into hole, kept from falling through by a backer that fits into the slot (a straight piece of wood, or something you're not afraid of messing up.) Clamp the backer (lightly) in place and apply an adhesive. JB Weld (or whatever the equivalent is up there in Leaf Land) will do fine. Superglue isn't great but it'll do in a pinch. Leave it to set up and you should have a working mag. You can drill out your patch and try again if it doesn't run.
Janky but quick: drill the dent out, tape over the hole in the slot from the inside, and slime that shit with JB Weld. Let it set up and remove the tape.
You might be able to just glue shimstock over the hole. Never tried it, don't know if the follower would try to snag on the edge of the (covered) hole or not.