Image is not showing on the product edit page after creating the product using API

I am trying to create a product with a product image on drupal using API. There was nothing given regarding uploading an image in API so I created a custom module under which i used this code to upload my image to the Drupal:

$data = base64_decode($encodedData['content']);
$file = file_save_data($data, 'public://astha.jpg');
$return['id'] = $file->id();

using this my image get uploaded to the following Drupal directory successfully:

mystore2/web/sites/default/files

Now, I used this $file->id() to pass it as target id for the image in the product body as follows:

...

"field_picture" => array:1 [
    "target_id" => "15"
  ],
...

The product gets created successfully and in response, I get the following data for the image added to the product:

...
"field_picture" => array:1 [
    0 => array:8 [
      "target_id" => 15
      "alt" => null
      "title" => null
      "width" => null
      "height" => null
      "target_type" => "file"
      "target_uuid" => "20d43ac4-1c47-4ba3-b373-16459efa5a7d"
      "url" => "/file/15"
    ]
  ]
...

But when I open the drupal admin panel, the image seems to be missing or corrupted.

What should I do now? I using Drupal version ^9.

Answers would be appreciated. Thanks.