The Capped-end Guide for Cavity-nesting Bees is a pictorial guide to what might be nesting in your house. Take a peek and see if anything looks familiar. While we cover the most common possibilities, another method is to do an image search on your favorite browser. This involves taking and uploading a photo into image search.
Chrome makes this very clear, with a camera icon on the right side of the search bar. For other browsers just type "image search" into your search bar and you should be taken to the image search area.
To be honest, if it isn't included in this pdf, your guess is likely as good as ours. Let us know if you discover a new species. Happy sleuthing!