Hi Ravi,

Please follow below example:-

In Apex, you can define top-level classes (also called outer classes) as well as inner classes, that is, a class defined within another class. You can only have inner classes one level deep. For example:

if you want to nested then aonther wrapper class should created sapratly
 

public class AccountSelectClassController{
 
    //Our collection of the class/wrapper objects wrapClass_1 
    public List<wrapClass_1> wrapAccountList {get; set;}
    public List<Account> selectedAccounts{get;set;}
     
    public AccountSelectClassController(){
        if(wrapAccountList == null) {
            wrapAccountList = new List<wrapClass_1>();
            for(Account a: [select Id, Name,BillingState, Website, Phone from Account limit 10]) {
                // As each Account is processed we create a new wrapClass_1 object and add it to the wrapAccountList
                wrapAccountList.add(new wrapClass_1(a));
            }
        }
    }
 
    public void processSelected() {
    selectedAccounts = new List<Account>();
 
        for(wrapAccount wrapAccountObj : wrapAccountList) {
            if(wrapAccountObj.selected == true) {
                selectedAccounts.add(wrapAccountObj.acc);
            }
        }
    }
 
 
    // This is our wrapper/container class. A container class is a class, a data structure, or an abstract data type whose instances are collections of other objects. In this example a wrapper class contains both the standard salesforce object Account and a Boolean value
    public class wrapClass_1 {
        public Account acc {get; set;}
        public Boolean selected {get; set;}
		Public List<wrapClass_2>nestedWrapperList = new List<wrapClass_2>();
 
        //This is the contructor method. When we create a new wrapAccount object we pass a Account that is set to the acc property. We also set the selected value to false
        public wrapClass_1(Account a) {
            acc = a;
            selected = false;
			 nestedWrapperList.add(new wrapClass_2(pass you object));
		   wrapClass_2 cls2 =  wrapClass_2();
			
        }
    }

New apex class : wrapClass_2

public class wrapClass_2 {
        public Contact con {get; set;}
        public Boolean selected {get; set;}
 
        public wrapClass_2(Contact a) {
            con = a;
            selected = false;
        }
    }

if you need any assistanse, Please let me know!!

Kindly mark my solution as the best answer if it helps you.

Thanks
Mukesh