how to allow user to input results in Array using java?
You have a lot of lines that do the same thing and which with a little rearranging can be consolidated:

int entrants = 0;
String[][] runners = null; //no need to create an array that you'll be throwing away
boolean valid = false; //this is for the initial number of runners question - it will stay false and keep us in the loop until a number between 2-7 is entered
System.out.println("Please enter the number of runners for this race (2 to 7 entrants permitted)");

do {
  //read the input
  entrants = input.nextInt();
  input.nextLine();

  //validate (we'll keep your messages)
  if(entrants &lt; 2) {
    System.out.println("You need at least 2 runners for a race, please re-enter the number of runners");      
  } else if (entrants &gt; 7) {
    System.out.println("You have entered too many runners for this race (max runners is 7). Please re-enter the number of runners");    
  } else {
    System.out.printf("You have entered %d runners\n", entrants);

    //create the array and set the exit condition
    runners = new String[entrants][2];
    valid = true;
  }
} while (!valid);


Note the use of a do-while which is like a while-loop but evaluates the condition after an iteration, i.e. the loop body is run at least once.

Further improvements could include putting the constraints into constants (i.e. min = 2 and max = 7) instead of having them in all over your code.