Validate String With /n linebreak one by one

I need to validate a string with line breaks in code it looks like this 01OXXB20\r\n5554569000000030\r\n5554569000000031\r\n5554569000000032\r\n5554569000000033\r\n5554569000000034\r\n5554569000000035\r\n5554569000000036\r\n5554569000000037\r\n5554569000000038\r\n5554569000000039

i need to validate for every linebreak if the number is less than 16 also i need to start validating starting from the 2nd linebreak so i will not read 01OXXB20