Yes! You can edit an entry you've published at any time. First, go to the entry that you want to edit, then look for the little blue "Edit" button at the top right (when your mouse is hovering somewhere over the entry, it turns blue to help you see it).
From there, a drop-down menu will appear. Click "Edit Entry."
You'll now have the ability to edit the text and add, edit, remove, or change the photos. Once you've made all the changes you'd like to see, click "Save Edits" to publish your updated entry.