errorMessage": "error:0909006C:PEM routines:get_name:no start line

I am having a key in AWS's AWS Secret Manager, that key has to be intended to use inside an .pem file and will look something like this:

-----BEGIN PRIVATE KEY-----
sdisfniwf
wnifiwf
-----END PRIVATE KEY-----

When I am using that key inside my Lambda function as a config parameter while I retrieve it as a String like this:

const config = {
      privateKey:JSON.parse(secret).PrivateKey;,
      region: region.toLowerCase()
 };

But I am constantly getting this error:

{
  "errorType": "Error",
  "errorMessage": "error:0909006C:PEM routines:get_name:no start line",
  "trace": [
    "Error: error:0909006C:PEM routines:get_name:no start line",
    "    at Sign.sign (internal/crypto/sig.js:103:29)",
    "    at c (/var/task/dist/getSession.js:2:3469)",
    "    at Object.signHeaders (/var/task/dist/getSession.js:2:4329)",
    "    at WebStoreClient.apiCall (/var/task/dist/getSession.js:2:473)",
    "    at WebStoreClient.getSession (/var/task/dist/getSession.js:2:1679)",
    "    at Runtime.e.handler (/var/task/dist/getSession.js:2:993556)",
    "    at processTicksAndRejections (internal/process/task_queues.js:97:5)"
  ]
}

Any idea on how I resolve this error?