progmem help

I don't get any errors apart from the line that says

sprintf_P(str1, hello[2]);

my full code below.

#include <avr/pgmspace.h>

prog_char hello[] PROGMEM =
{
  "HELLO1"
  "HELLO2"
  "HELLO3"
};
void setup()
{ 
 //Initialize serial and wait for port to open:
  Serial.begin(9600); 
  while (!Serial)
  {
    ; // wait for serial port to connect. Needed for Leonardo only
  }
}

void loop()
{
  char str1;
  
  sprintf_P(str1, hello[2]);
  
  Serial.print(str1);
  
  delay(5000);
}

Am wanting to have an array of strings and read them when i want. Just trying to learn about progmem.