In this 15 date is as selected in datepicker i want to disable all the dates before 15th october
Try using the option of minimum date - Ref jquery - Yii2 jui datepicker range not working - Stack Overflow
Since this data is coming from the database, the above option may work to sent the minimum date by reading the current value. Also you can see if there is a client option for it that you can set using JavaScript - again based on database value.
The other suggestion (also something that is best to implement for security) would be to compare existing database value and new entered value, on post, and do a server level validation.
Thanks i have solved it by putting the date in hidden field and make it as minDate in datepicker option and it worked.