Using Salesforce API in a webapp that SSO via redirect URI

My client would like to facilitate/automatize their web user registration. Currently they ask the registrant to fill in a web form and then submit it. This is the way they thought we can go with (the following is really a high level overview):

  1. sign in via OKTA SSO (redirect uri)
  2. get user data from Salesforce via their REST/SOAP API
  3. fill in and submit the client’s registration form with the user data
    Is there a way, that after SSO into OKTA (okta hosted login) via a webapp - and so after getting the JWT/access token - I can access Salesforce user data via Salesforce Rest/SOAP API? It seems Salesforce REST API expect to have a Bearer token in the request header.
    For testing this flow, I have already set up a sandbox Salesforce app integration (with Provisioning), the webapp OAuth2 integration in my OKTA Admin and implemented the SSO flow in my webapp (which works) so I have the access token. How to go from this point? How can I use the access token to request user data via Salesforce REST API calls? Can I generate somehow a bearer token that I can use for this purpose? If not, how can I access the Salesforce User info?
    Thank you