1. A method for expanding a size of a field associated with a plurality of variables present in a source code of at least one software application, the method comprising processor implemented steps of: receiving said source code in at least one source language; parsing said source code to generate an abstract syntax tree (AST), wherein the AST comprises relation amongst the plurality of variables, and wherein the relation is stored in a repository; identifying a first set of seed variables from the plurality of variables, wherein the first set of seed variables is identified based on, a) matching of a pattern pertaining to the field received from a user with patterns of fields associated with the plurality of variables, or b) one or more files, one or more database fields, or one or more screen fields; performing multi-level impact analysis on the first set of seed variables in order to identify a second set of seed variables, wherein performing the multi-level impact analysis further comprises excluding one or more seed variables from the second set of seed variables, wherein the one or more seed variables indicative of non-impacted variables, and wherein the exclusion of the non-impacted variables facilitates in reduction of the false positives; generating an analysis report comprising the first set of seed variables and the second set of seed variables, wherein the analysis report facilitates to further exclude at least one seed variable from the first set of seed variables or the second set of seed variables in order to derive a set of impacted variables, thereby further facilitating to reduce the false positives; and expanding the size of a field associated with each seed variable of the set of impacted variables.