Hello @Carole1221
Well that's a pretty harsh start if this was your first guest😓
We used to be able to claim for damages for stained sheets but Airbnb have changed their policy and consider it as part of doing business.
Stained sheets are part and parcel of this business I'm afraid and I can't tell you how many hours I have spent trying to get them out of my sheets but the key to getting them out is to treat them BEFORE you put them in the machine as some stains will be sealed into the fabric once they hit the hot water in the cycle.
You're starting out so you really need good reviews and any claim you make (it goes first to the guest by the way to accept or refuse) will undoubtedly result in a lower than average score and review so personally I would abstain. Don't mention it to the guest either, let them think that you're a fab host and hopefully they'll give you a great review.
What colour are these sheets? If white, there are loads of options on the net but it would help to know what kind of stain it is. Could it be a tanning product maybe?