How can I implement collisions in OpenGL using C?

I am making a simple game demo to get me started on openGL but I do not know where to start when implementing collisions. I have looked on the internet to see if there is a function to do it for me but I cant seem to find it. Do I have to make my own collision sistem? If so where can I start. I am trying to make my player collide with the walls arround him.

Code:

#include <stdio.h>
#include <stdlib.h>
#include <GL/glut.h>

#define or ||
#define and &&

int width=1000; //Screen width
int height=500; //Screen height
int px=100; //Player pos x
int py=100; //Player pos y

//-----------------------------MAP----------------------------------------------
#define mapX  8      //map width
#define mapY  8      //map height
#define mapS 64      //map cube size

int map[]={           //the map array. Edit to change level but keep the outer walls
 1,1,1,1,1,1,1,1,
 1,0,1,0,0,0,0,1,
 1,0,1,0,0,0,0,1,
 1,0,1,0,0,0,0,1,
 1,0,0,0,0,0,0,1,
 1,0,0,0,0,1,0,1,
 1,0,0,0,0,0,0,1,
 1,1,1,1,1,1,1,1,   
};

void drawPlayer(int px,int py){
 glColor3f(1,1,0);
 glPointSize(8);
 glBegin(GL_POINTS);
 glVertex2i(px,py);
 glEnd();
}

void drawMap2D(){
 int x,y,xo,yo;
 for(y=0;y<mapY;y++){
  for(x=0;x<mapX;x++){
   if(map[y*mapX+x]==1){glColor3f(1,1,1);} else{glColor3f(0,0,0);}
   xo=x*mapS; yo=y*mapS;
   glBegin(GL_QUADS); 
   glVertex2i( 0   +xo, 0   +yo); 
   glVertex2i( 0   +xo, mapS+yo); 
   glVertex2i( mapS+xo, mapS+yo);  
   glVertex2i( mapS+xo, 0   +yo); 
   glEnd();
  } 
 } 
}

void Buttons(unsigned char key,int x,int y){
 if(key=='a'){px-=5;}   
 if(key=='d'){px+=5;} 
 if(key=='w'){py-=5;}
 if(key=='s'){py+=5;}
 glutPostRedisplay();
}

void display(){
 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 //-----------------------Draw----------------------
 drawMap2D();
 drawPlayer(px,py);
 //-------------------------------------------------
 glutSwapBuffers();
}

void init(){
 glClearColor(0.3,0.3,0.3,0);
 gluOrtho2D(0,width,height,0);
}

int main(int argc, char** argv){ 
 glutInit(&argc, argv);
 glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA);
 glutInitWindowSize(width,height);
 glutCreateWindow("OpenGL");
 init();
 glutDisplayFunc(display);
 glutKeyboardFunc(Buttons);
 glutMainLoop();
 return 0;
}