error:"tsdb.HandleRequest() error Get x509: certificate signed by unknown authority"

When hitting Test Rule in grafana, I am getting below error message. Even though alert email is coming but no metric information in coming in the email body and stating the same error message as below. Both grafana and prometheus are hosted on openshift container using docker image. Please suggest where/how to add certs that could resolve the issue. TIA

error:“tsdb.HandleRequest() error Get{namespace%3D"pdc-alpha"%2C+phase%3D"Pending"})&start=2020-08-21T11%3A56%3A49.321739205Z&step=15.000: x509: certificate signed by unknown authority”