I won a region locked game that wasn't marked as such

write about it in giveaway comments section

I would just tell him in comments section and ask to reroll for someone else to win it.

just ask for reroll, but first try to add it anyway since sometimes those keys are actually ROW (something like HB bundle last time)

if there is description of "provider's rule", correspondence will change depending on the condition.
For example, in the case of "region lock", it is permission to delete or re-roll.

Normally, is it like this?

1. Tell the region lock.
2. If you give up, please allow reroll.
3. If you can not receive it within one week.
   If you do not give up, ask if you can receive alternative key offerings.
4. If you can not receive the offer, consult with support.

I think it's best if he deletes it since there must be a lot of people like me who entered the ga not knowing it's region locked and if he reroll it would probably just get another user who can't activate it, i'll try to get his attention on the comments thank you for your help

Ask support to delete the giveaway. They can also tell you what regions it´s for, it happened to me recently and that´s what they did.