@SFD13 you can surely delete the index if you are re-ingesting the whole dump of data again into ES. When filebeat pushes the logs, ES will anyway check if the index is present or not, and if not, it is going to create a new index for you.
The only issue here could be if there some specific index name you might be using in your application, in which case, the index name could be set on filebeat configuration.
PS: there is no point in deleting all the data and keeping the index. ES only creates an index when the very first document/ event/ log for the index is ingested and stored.