@Rebekah189
Sorry your sofa is stained! How frustrating!
What would I do? It depends on the stain. First I'd do my best to clean it myself, after finding out what it is. I keep a variety of cleaning items, especially for upholstery issues, and for our leather recliner chair...they've all worked well for me in the past. If the type of stain is not obvious, I'd ask the guest for help, respectfully, of course. A good source for information is always online, from my cleaning help, and the local dry cleaners, who always know these things. A stain on anything is cost of doing business imho, and a learning experience for me. In the past decades I've learned a lot of tricks around stains - including food and candy tucked in the couch.
Best of luck to you with this, and please let us know the results!