There are many definitions of what it means to be an expert. Everyone likes to be seen as an expert, but many don't feel worthy of the title. This feeling of being unworthy relates to the "Imposter Syndrome" where an individual feels inferior because they constantly compare their single self to everyone else's combined selves. While it's really not possible for everyone to be "THE" expert, it's an absolute constant that everyone is "AN" expert is some fashion.
Are you "AN" expert? Yes.
Am I "AN" expert? Yes.
Are either of us "THE" expert? No.
Is it possible to be "AN" expert in everything? No.
Is it possible to be "AN" expert in a single topic? Yes.
Expert != Expert == Expert
Everyone is an expert in some area at some time, but not in all areas at all times. What this means is that any single person will always know at least a little more than someone else. It's likely that you'll rarely be "THE" expert in a given room of people, but there will be times that you are. Never be discouraged by this. Be confident in yourself, in your knowledge, and in your abilities. If you have knowledge to contribute and wisdom to part unto other, then do it. If you can learn from others, then do it. Don't let the perceived "expertness" of yourself or other hold back the potential for progress and learning.
An expert knows when to go and when to stop. Be that expert. Remain humble.