Hi Mahesh,
I agree with Vengal B. The problem is not related to RSKC settings, it is a general check that the string should not start with an exclamation mark.
However, instead of editing the record in the PSA, I suggest to implement an add-on for cleansing character strings. Please read my blog Introducing an Add-on for Cleansing Character Strings where you can find all details for such an approach and a link to the document with implementation instructions.
Best regards,
Sander