Puffy Sleeve One Shoulder Dress

Purchased 10+ years ago from Forever 21 and only worn once (on NYE), this one shoulder, puffy sleeve dress is so cute. Silk like material with lining and has pockets!! There is a stain on the backside (not sure where it came from but is NOT blood. I’m thinking dirty water that discolored over the years). I have not tried washing it; I feel like it would come out with wash or dry clean. Size xsmall, fits like a small small