According to the Maryland Motor Vehicle Administration (MVA) out-of-state learner's permits cannot be exchanged for a Maryland Learner's Permit or License.

To get a learner’s permit in Maryland here is some of the pertinent information:

• Minimum age for applicants is 15 years and 9 months.
• If under 16, you must provide a completed Learner's Permit School Attendance Certification form (DL-300) to an MVA official during the learner's permit application process.
• You must pass a vision test and knowledge test.
• If under 18, a parent or guardian must sign the application or, if the applicant has no parent or guardian or is married, an adult employer of the applicant or any other responsible adult may cosign the application.
• You must be 18 to obtain a Learner's Permit for a CDL Intrastate, 21 years of age for Interstate. In addition, you must also have a full driver's license (does not include a motorcycle license).
• You will be required to disclose your social security number. Applicants not eligible for a social security number will be required to provide a self-certification.
• A valid U.S. Department of Transportation physical card (if applying for a Learner’s Permit to drive a commercial motor vehicle).
• You must also complete the Maryland Graduated Licensing System requirements.

So it does not appear that you nephew can transfer his New York State learner's permit for a Maryland Permit but will have to start over with the graduated licensing process in MD. The Rookie Driver process in MD applies to all applicants, regardless of age, who have never held a license in Maryland or any other state or country or who have held their out-of-state license for less than eighteen (18) months.

You or your nephew can contact the MD MVA for more information on how he can get started on the graduated licensing system in Maryland so he can get a MD permit and start driving again. Remember while driving, learner's permit holders must be accompanied by a qualified supervising driver who is 21 years or older, and has held a license for a minimum of 3 years. The person must be seated beside the new driver at all times, with no other front seat occupants.