Mistake in resume sent; what to do?
You are risking drawing attention to a mistake that could otherwise go unnoticed. 

Is resume the main part of the application? Or are there other parts, like an essay, recommendation letter, some all-important exam (like GRE for graduate study)? 

Also, if there is time till deadline, consider waiting few days and then updating the resume with some new bit of information, like more detailed description of an experience that they might find relevant. An update to content is a lot more acceptable than fixing typos.