Search char in an exat string with pointer

So simple,just for ex.

#include <stdio.h>
char *find_char(char const *source,char const *chars);
int main(void){
    char *source="hellopnig0s";
    char *chars="epg0";
    char *result;
    result=find_char(source,chars);
    if(result){
        printf("We found %c in position:%p\n",*result,result);
    }else{
        puts("Nothing be found.");
    }
}
char *find_char(char const *source,char const *chars){
    char * check;
    while(*chars!='\0'){
        while(*source!='\0'){
            if(*source++==*chars){
                return source-1;
                break;
            }else{
                check=NULL;
            }
        }
        chars++;
    }
    if(!check){
        return check;
    }
}