Depends on the situation. If it's something that was accidental and you live up to it and can show that you learned something, then no biggie. However if it is something tied to negligence/stupidity, then that's another story altogether.

I have a friend that taxiied into a truck while training towards their commercial pilot certificate. He's now a Captain at Mesaba and was just hired at FedEx. No Biggie.

Care to elaborate on your situation?