Unable to present accepted conference paper after mentioning it on submitted applications
If this is something like a doctoral symposium in which papers are discussed but not printed in the proceedings, then you should just inform everyone who matters of the situation. It shouldn't be a problem. Acceptance actually means something in a situation like this. And you can always, in this case, submit the paper elsewhere if it doesn't appear or if acceptance is withdrawn by the committee due to not being able to attend. 

On the other hand, if the paper will be in the proceedings whether you are there or not, which may be the case in CS, then you don't really need to do anything. You could still inform people, but the acceptance for the conference and publication in the proceedings is all that is really required. 

But in general honesty and forthrightness is a plus.