02/16/2009 at 05:35 PM EST
Less than an hour after a South Carolina sheriff said he would not file drug charges against Michael Phelps, Olympic star – who was photographed last fall smoking a marijuana pipe
– issued another mea culpa
and pledged to "dive back into the pool."
"I'm glad this matter is put to rest. But there are also some important lessons that I've learned," Phelps, 23, said in a statement Monday.
"For me, it's all about recognizing that I used bad judgment and it's a mistake I won't make again. For young people especially – be careful about the decisions you make. One bad decision can really hurt you and the people you care about."
Richland County sheriff Leon Lott announced earlier Monday that a nearly two-week investigation had failed to produce enough evidence to prosecute anyone present at a November party at the University of South Carolina, where the photo was taken.
– Melody Simmons