Leaking fridge- how can i mend it?

I've had a hotpoint RLA30 fridge for 3years and had no probs with it until very recently. It keeps leaking water onto the floor of the fridge. I'm sure from searching this site that it's something to do with the drainage hole because the water seems to be gathering on top of the hole but I'm not sure how to go about fixing it. I would greatly appreciate it if someone could offer me some advice about how I can fix this as my 17month old son is having too much fun playing in the puddle at the bottom of my fridge!