New York (CNN) -- A New Jersey man who breached airport security to give his girlfriend a kiss, causing scores of flight delays, pleaded guilty Tuesday to defiant trespass, his lawyer said.

Haisong Jiang, 28, pleaded guilty to a charge that is a "petty disorderly persons offense ... it's below a crime, it's not even considered a crime in New Jersey," his lawyer, Eric B. Bruce said.

Jiang apologized. "I made big mistake, and I also learned a big lesson in my life," he told reporters after the court appearance.

Bruce said that Jiang, a Rutgers University Ph.D. candidate who is originally from China, ducked under a rope and entered a security area at Newark Liberty International Airport on January 3 to give his girlfriend a kiss. The security breach shut down Terminal C for hours and forced the rescreening of thousands of passengers. Scores of flights were delayed.

Jiang will have to pay a $500 fine and court fees and costs of $158, as part of a plea deal reached with prosecutors, Bruce said. He also will have to perform 100 hours of community service.

He is "very relieved," Bruce said. He said the nature of Jiang's community service has not yet been determined.

"We hope it'll be at a hospital, soup kitchen, medical clinic, something like that," he said.

Jiang was arrested on January 8, several days after the security breach. Security video from the incident shows a Transportation Security Administration officer who left his post unattended a few minutes after he asked an unidentified man in a light-colored jacket to stay behind the rope line. Moments later, the man ducks under the rope and walks the wrong way through security to greet a woman.

The lawyer said Jiang and his girlfriend, who lives in California, are still together. "They are still together, and they are still very much in love," he said.

Bruce said the charge will appear on Jiang's record.

"It can be expunged after, I believe, five years. It's an arrest, it's going to show on his record, but it's a very minor infraction," he said.

The lawyer said that the incident will not affect Jiang's immigration status, CNN affiliate News 12 New Jersey reported.

He will likely finish his Ph.D. at Rutgers in May or June, Bruce said. Jiang is doing research on a cure for glaucoma, cataracts and other eye diseases.

After the security breach, TSA said it would use the incident as a "hard lesson" to reinforce a "sharp focus and tight discipline" at the agency's stations across the country.

The incident also prompted Sen. Frank R. Lautenberg, D-New Jersey, to introduce legislation that would create a civil penalty of up to $10,000 for intentionally breaching airport security and a criminal penalty of up to 10 years in prison.

It would also mandate the use of security cameras at all airport terminal checkpoints and secure area exits at every U.S. airport. Although the cameras are now recommended for airports, Lautenberg said they are not mandated by law.

Soon after the security breach occurred, Lautenberg had called on the person who had caused the breach to turn himself in, saying "You've committed what essentially is a crime."