If its a very slight wiggle I woulnt worry about it. Balance it till it stays in any position. When you tighten up the prop nut try to hold it centered, basically not let the sides touch the shaft. If you have a significant wiggle these are your options;
1. The easiest is to dry your tears and buy a
new one, lesson learned.
2. Try what has been suggested above. Definately use a reamer by hand from the back!
3. This is hard and a last resort. And if your super cheap and can't admit defeat like me! I've filled in the hole with epoxy such as five minute. Find the center ( measure the hub an x, and from tip to tip. if it's it's not wood you can use the rings on the back an measure the center) and start with a small drill bit till I get the reamer started. If its off a fraction it's ok because you more concerned with the balance point shifting when you mount it. Blade track of a 16th or two will matter little on an R/C.
4. Paint it up all shiny with an old spinner painted ip all shiny mount it to a piece of finished wood and you have a nice static display! I have a room full of them, like a big game trophy room!