Monetary compensation help

so first off, I am a hobbyist. I took my camera to a local wrestling event, posted it on IG, and a wrestler messaged me told me he liked the photo and wanted a copy. I told him all I ask for is credit if using it for promo purposes. well fast forward a day later and he posted the photo, credited me like I asked, but also put 8x10s coming soon. assuming he's going to sell them and not give them away. now, since I never mentioned in the original conversation about compensation for usage, is it too late? or should I send him a message telling him that if he wants to use it to sell promo photos we can work out a deal. and if so what would be a reasonable asking price for usage?.thank you in advance for the help !