When a client calls or walks in wanting something that you don't know how to do OR aren't too good at doing yet, it's okay to refer them to someone who has the experience to get it done. It doesn't diminish your abilities, in fact, it speak volumes about your character and integrity.
You never know, they may then request something you are good at. Honesty is always the best policy when dealing with potential clients. That, and clear communication. 💋