This WILL happen. It doesn't matter how good you are or the quality of your tools, but if you use nib pens or brushes you WILL get an accidental spill sometimes.
That said, I've found it really help to have a piece of scrap paper nearby. Whenever I dip my nib I make a mark on the scrap piece. Not only does this make the ink start to flow, but also help if you've overloaded your nib. The excess ink will spill onto the scratch paper instead of your artwork.
Might seem like a lot of extra work to do this after everytime you load the nib, but it very soon become second nature.
Oh, and I suggest you get some "Deleter White 2". It's fairly cheap from Amazon, and works wonders for correcting spills and errors. Way better than the white acrylic I tried to use when I started out inking.