Oops! It happens to us all at some point I guess
The advice given so far is great- just wash it with your nappy load a few more times before using it again.
You could try and add a tablespoon of white vinegar in your fabric softner drawer of the nappy wash. This willl help keep your nappies soft and cuts through any detergent left on by previous washes. I live in a hard water area so this is essential to avoid crunchy nappies!
You do need to use white
vinegar though (can get a 1/2 litre bottle from asda for less than 60p) the malt vinegar you use on your chips is no good
Using a splash of white vinegar does not make your nappies smell of chips either lol
Hope that helps