So I've booked a round trip Monday to Thursday (CLE-SFO-CLE). I was planning on renting a car and driving up to Windsor, CA and back, but looking into it I realized there is quite a bit of hassle involved.

If I were to book another Round trip United Itinerary SFO-STS-SFO in the middle of my trip to California, would that violate some strange United rule on nesting tickets? Forgive me for such a newbie question, but most of my travel is international and I've never had this situation arise.