Trying to access array offset on value of type bool error

In PHP you do not need to initialize arrays. PHP makes array usage extreemly simple

While loops will stop when a false is returned from the fetch, so no limit on rowcount is needed.

So amend the code to

$conn = new mysqli('localhost','root','','project_nlt');
$qry = "select * 
        from useri_nfo 
        where skills='$skill' 
        order by u_id ASC";
if ($row = $conn->query($qry)) {
    while ($r = $row->fetch_array(MYSQLI_ASSOC)) {
        //echo $r; you cannot echo an array, try `var_dump() or print_r()

        $name[]         = $r['user_name'];
        $profile_img[]  = $r['dp'];
        $skills[]       = $r['skills'];
        $address[]      = $r['address'];
    }
}

Your script is open to SQL Injection Attack. Even if you are escaping inputs, its not safe! You should consider using prepared parameterized statements in either the MYSQLI_ or PDO API's instead of concatenated values

So this should really be coded as

$conn = new mysqli('localhost','root','','project_nlt');
$qry = "select * 
        from useri_nfo 
        where skills = ?  
        order by u_id ASC";
$stmt = $conn->prepare($sql);
$stmt->bind_param('s', $skills)
$stmt->execute();
$result = $stmt-<get_reslt();

while ($r = $result->fetch_array(MYSQLI_ASSOC)) {
    //echo $r; you cannot echo an array, try `var_dump() or print_r()

    $name[]         = $r['user_name'];
    $profile_img[]  = $r['dp'];
    $skills[]       = $r['skills'];
    $address[]      = $r['address'];
}