AWS Cognito issue while login with custom OpenID Connect

Question

I have created "Salesforce" login using the OpenID Connect in AWS Cognito. Now after setting everything when I login user using Cognito Hosted UI and after that user successfully login it redirect back to my redirect_url and it comes with a code that I exchange it with this endpoint

$url  = {MY_COGNTIO_DOMAIN}/oauth2/token
$data = [
        'form_params' => [
            'grant_type' => 'authorization_code',
            'client_id' => "COGNITO_CLIENT_ID",
            'client_secret' => "COGNITO_CLIENT_SECRET",
            'code' => $code,
            'redirect_uri' => $redirectUri,
        ],
    ];
post request($data)

now this post reqeust returns the id_token, and access_token. This is valid token and also my user got registered automatically on User Pool. Now my issue is that when I login a user without Cognito Hosted UI and it came back to my redirect_url after success login but when i run the exchange api with previous post data it does not work. I have to change the client_id and client_secrect from Cognito to Salesforce. also the Endpoint needs to be change

$url  = https://login.salesforce.com/services/oauth2/token
$data = [
        'form_params' => [
            'grant_type' => 'authorization_code',
            'client_id' => "SALESFORCE_CLIENT_ID",
            'client_secret' => "SALESFORCE_CLIENT_SECRET",
            'code' => $code,
            'redirect_uri' => $redirectUri,
        ],
    ];
post request($data)

then it returns the id_token, and access_token but this access_token is not valid like it does not contains the user pool registerd data also in this way my user does not registerd automatically. Kindly suggest what should I do. I have already spent alot time on this.

So by using the Hosted UI it works fine but when I do login programatically then it works but the token is not a valid user pool token