HI Abhijeet,
Discovery, checkout, build, and analysis of a PR is the responsibility of a CI system. SonarQube has no automatic facility to discover and analyze PRs by itself, whereas a CI system like Jenkins with the proper plugins installed does.
We have documentation covering our integration with Jenkins + GitHub that could make this possible.
To be clear, I’m not advocating for Jenkins, just mentioning it because the integration is easy and free.