How to use a block as a field in Drupal 7 I'm working with this module which is providing me a block for uploading the file as mentioned in the doc https://drupal.org/project/jquery_file_upload

Is there a way, where I can use this block as a field while adding the content, for instance at node/add/[my_custom_content]
No, fields are totally independent concept than blocks. Of course there is a way to have a region inside field, and you could then drop that block to region, but there would be no connection between block's uploading capabilities and created node.

If you have a fancy file uploading requirements, it would be better to write them down and ask what module can do it for your file or image field.