How to handle CORS to handle traffic between https and http

Hello Every body,
I am quite new to Tyk,

i setup Tyk to run on https, in my API I am setting up target url like this

however my public url is like this https://mypublicurl/api1

so Browser stopping the request due to Cors ,
i am not understanding how can if fix this

ccess to fetch at ‘https://api.xxxx/api’ (redirected from ‘http://api.xxxx/api’) from origin ‘null’ has been blocked by CORS policy: The ‘Access-Control-Allow-Origin’ header contains multiple values ‘null, *’, but only one is allowed. Have the server send the header with a valid value, or, if an opaque response serves your needs, set the request’s mode to ‘no-cors’ to fetch the resource with CORS disabled.