Both are interrelated.

1) Regression Testing is a Testing Technique that we use to 
validate/ensure that the earlier tested module doesn't lead 
to any defects after the integration with other 
modules.Means it works properly after integration.

2)Validation is the major thing in the whole process, Based 
on that we decide whether the product meet the SRS, and 
ready for deployment...

Validation: validation is main testing of the application. 
the execpected results need to check with actual results.

Regression: Re execution of the test cases on modified 
build is called Regression testing.