May & July light jacket

May & July brand light jacket Purchased from red dress boutique Size medium with relaxed fit (misses or junior fit so would fit sizes 2-8) Stain on back that appeared early in ownership. It hasn’t been worn much. I don’t know what it is and I can’t remove it but it really isn’t noticeable when wearing. Maybe you can remove with a stain remover- I’m not skilled in that area Because of this I will review offers to sell